feat: Add studio development/feature documentation.

* Document setting up studio for a new keyboard definition.
* Document how to enable ZMK Studio for a build, adding reserved layers,
  and controlling which behaviors are built into a studio firmware.

docs/docs/config/studio.md

@@ -0,0 +1,35 @@
+---
+title: ZMK Studio Configuration
+sidebar_label: ZMK Studio
+---
+
+:::warning[Alpha Feature
+]
+ZMK Studio is still in active development, and the below information is for development purposes only. For up to date information, join the [ZMK Discord](https://zmk.dev/community/discord/invite) server and discuss in `#studio-development`.
+
+:::
+
+The following settings affect the ZMK Studio portions of ZMK. See the [ZMK Studio Feature](../features/studio.md) for more information on enabling and building with ZMK Studio enabled.
+
+See [Configuration Overview](index.md) for instructions on how to change these settings.
+
+## Kconfig
+
+Definition file: [zmk/app/src/studio/Kconfig](https://github.com/zmkfirmware/zmk/blob/main/app/src/studio/Kconfig)
+
+### Locking
+
+| Config                                    | Type | Description                                                                         | Default |
+| ----------------------------------------- | ---- | ----------------------------------------------------------------------------------- | ------- |
+| `CONFIG_ZMK_STUDIO_LOCKING`               | bool | Enable/disable locking for ZMK Studio                                               | y       |
+| `CONFIG_ZMK_STUDIO_LOCK_IDLE_TIMEOUT_SEC` | int  | Seconds of inactivity in ZMK Studio before automatically locking                    | 500     |
+| `CONFIG_ZMK_STUDIO_LOCK_ON_DISCONNECT`    | bool | Whether to automatically lock again whenever ZMK Studio disconnects from the device | y       |
+
+### Transport/Protocol Details
+
+| Config                                         | Type | Description                                                                   | Default |
+| ---------------------------------------------- | ---- | ----------------------------------------------------------------------------- | ------- |
+| `CONFIG_ZMK_STUDIO_TRANSPORT_BLE_PREF_LATENCY` | int  | Lower latency to request while ZMK Studio is active to improve responsiveness | 10      |
+| `CONFIG_ZMK_STUDIO_RPC_THREAD_STACK_SIZE`      | int  | Stack size for the dedicated RPC thread                                       | 1800    |
+| `CONFIG_ZMK_STUDIO_RPC_RX_BUF_SIZE`            | int  | Number of bytes available for buffering incoming messages                     | 30      |
+| `CONFIG_ZMK_STUDIO_RPC_TX_BUF_SIZE`            | int  | Number of bytes available for buffering outgoing messages                     | 64      |

docs/docs/development/studio-setup.md

@@ -0,0 +1,80 @@
+---
+title: Studio Setup
+---
+
+:::warning[Alpha Feature]
+
+ZMK Studio support is in alpha at this point. Although our best efforts are being made to keep compatibility during active development, but is not guaranteed.
+
+:::
+
+This guide will walk you through enabling ZMK Studio support for a keyboard.
+
+The main additional pieces needed for Studio support involve additional metadata needed in order
+to properly to display the physical layouts available for the particular keyboard.
+
+# Physical Layout Positions
+
+Physical layouts are described as part of the [New Shield Guide](./new-shield.mdx#physical-layouts), but additional possible property is not described there. The `keys` property is used to describe the physical attributes of each key position present in that layout, and are listed in the same order as keymap bindings, matrix transforms, etc. The properties available are:
+
+- Width
+- Height
+- X
+- Y
+- Rotation
+- Rotation X
+- Rotation Y
+
+All X/Y/Width/Height values are in "key unit" units, with a 100th of a key unit resolution. Rotations are in degrees, with a 100th of a degree resolution. Due to the nature of devicetree, all values are stored in the devicetree without decimals as hundredths of a value, e.g. one key unit is represented as `100`, twenty degrees is represented as `2000`, etc.
+
+Here is an example physical layout for a 2x2 macropad:
+
+```
+    macropad_physical_layout: macropad_physical_layout {
+        compatible = "zmk,physical-layout";
+        display-name = "Macro Pad";
+
+        keys  //                     w   h    x    y     rot    rx    ry
+            = <&key_physical_attrs 100 100    0    0       0     0     0>
+            , <&key_physical_attrs 100 100  100    0       0     0     0>
+            , <&key_physical_attrs 100 100    0  100       0     0     0>
+            , <&key_physical_attrs 100 100  100  100       0     0     0>
+            ;
+    };
+```
+
+# Position Map
+
+When switching between layouts with ZMK Studio, the keymap of the previously selected layout is used to populate the keymap in the new layout. To determine which keymap entry maps to which entry in the new layout, keys between the two layouts are matched that share the exact same physical attributes. However, in some cases, keys between layouts are not in exactly the same position.
+
+For those cases, a position map is used. The position map includes a sequence for every relevant layout, and the corresponding entries in the `positions` will be used to determine the mapping.
+
+For example, the following position map correctly maps the 5-column and 6-column Corne keymap layouts.
+
+```
+    foostan_corne_position_map {
+        compatible = "zmk,physical-layout-position-map";
+
+        complete;
+
+        twelve {
+            physical-layout = <&foostan_corne_6col_layout>;
+            positions
+                = <    1  2  3  4  5  6  7  8  9 10   >
+                , <   13 14 15 16 17 18 19 20 21 22   >
+                , <   25 26 27 28 29 30 31 32 33 34   >
+                , <         36 37 38 39 40 41               >;
+        };
+
+        ten {
+            physical-layout = <&foostan_corne_5col_layout>;
+            positions
+                = < 0  1  2  3  4  5  6  7  8  9>
+                , <10 11 12 13 14 15 16 17 18 19>
+                , <20 21 22 23 24 25 26 27 28 29>
+                ,       <30 31 32 33 34 35>;
+        };
+    };
+```
+
+The first entries in the two mappings have values `1` and `0` respectively, which means that the zero-th entry in the 5-column will map to the first entry in the 6-column layout, the second entries show that the second 6-column keymap entry corresponds to the first 5-column entry, etc.

docs/docs/features/studio.md

@@ -0,0 +1,109 @@
+---
+title: ZMK Studio
+sidebar_label: Studio
+---
+
+:::warning[Alpha Feature]
+
+ZMK Studio support is in alpha at this point. Although our best efforts are being made to keep compatibility during active development, but is not guaranteed.
+
+:::
+
+ZMK Studio provides runtime update functionality to ZMK powered devices. Studio is still under active development, and is not yet ready for casual end user use.
+
+## Building
+
+Building for ZMK Studio involves two main additional items.
+
+- Build with the `studio-rpc-usb-uart` snippet to enable the endpoint used for Studio communication over USB.
+- Enable the `ZMK_STUDIO` Kconfig setting.
+
+### GitHub Actions
+
+First add a `studio-rpc-usb-uart` to the `snippet` property of your build configuration. For a split keyboard, you should do this _only_ for your central/left side, e.g.:
+
+```
+---
+include:
+  - board: nice_nano_v2
+    shield: corne_left
+    snippet: studio-rpc-usb-uart
+  - board: nice_nano_v2
+    shield: corne_right
+```
+
+Next, enable the `ZMK_STUDIO` Kconfig symbol, for example by adding the following line to your .conf file:
+
+```
+CONFIG_ZMK_STUDIO=y
+```
+
+### Local Build
+
+When building locally, use the `-S` parameter to include the `studio-rpc-usb-uart` snippet, and append the `ZMK_STUDIO` Kconfig as an additional CMake argument, e.g.:
+
+```bash
+west build -d build/cl_studio -b nice_nano_v2 \
+  -S studio-rpc-usb-uart -- -DSHIELD=corne_left -DCONFIG_ZMK_STUDIO=y
+```
+
+## Behaviors
+
+Normally, ZMK will only build and include behaviors that are referenced by your keymap, and unused behavior will be skipped. However, studio builds using the `studio-rpc-usb-uart` snippet will automatically define the `ZMK_BEHAVIORS_KEEP_ALL` value, which changes the approach and builds all possible behaviors into the firmware.
+
+A few controls are available to override this behavior for fine-grained control of what behaviors are built. Behaviors can be kept or omitted by defining certain values in the top of your keymap file before the standard `behaviors.dtsi` file is included.
+
+### Omit Specific Behaviors
+
+You can omit a specific behaviors by defining a variable like `ZMK_BEHAVIORS_OMIT_FOO` at the top of your keymap:
+
+```dts
+#define ZMK_BEHAVIORS_OMIT_KEY_TOGGLE
+
+#include <behaviors.dtsi>
+```
+
+### Keep Only Selective Behaviors
+
+To override the default "keep all" functionality, you can define the `ZMK_BEHAVIORS_KEEP_SELECTIVE` flag, and then keep only specific behaviors with a flag like `ZMK_BEHAVIORS_KEEP_FOO`, e.g.:
+
+```dts
+#define ZMK_BEHAVIORS_KEEP_SELECTIVE
+
+#define ZMK_BEHAVIORS_KEEP_STICKY_KEY
+#define ZMK_BEHAVIORS_KEEP_MOD_TAP
+
+#include <behaviors.dtsi>
+```
+
+## Layers
+
+By default, a build with ZMK Studio enabled will only allow as many layers as are defined in your standard keymap. To make additional layers available for use through Studio, you simply add new empty layers to your keymap with a status of `reserved`, e.g.:
+
+```dts
+/ {
+    keymap {
+        compatible = "zmk,keymap";
+
+        base {
+            display-name = "Base";
+            bindings = // etc.
+        };
+
+        fn_layer {
+            display-name = "Fn";
+            bindings = // etc.
+        };
+
+        extra1 {
+            status = "reserved";
+        };
+
+        extra2 {
+            status = "reserved";
+        };
+    }
+}
+```
+
+The reserved layers will be ignored during regular ZMK builds, but come available for ZMK Studio enabled builds.

docs/sidebars.js

@@ -44,6 +44,7 @@ module.exports = {
         "features/backlight",
         "features/battery",
         "features/soft-off",
+        "features/studio",
       ],
     },
     {
@@ -112,6 +113,7 @@ module.exports = {
         "config/power",
         "config/underglow",
         "config/system",
+        "config/studio",
       ],
     },
     {
@@ -144,6 +146,7 @@ module.exports = {
             "development/new-shield",
             "development/hardware-metadata-files",
             "development/new-behavior",
+            "development/studio-setup",
           ],
         },
       ],