feat(behaviors): Add soft off behavior.

* New soft-off behavior that can be used to force the device
  into  soft-off state with only certain configured wakeup
  devices.

app/CMakeLists.txt

@@ -54,6 +54,7 @@ if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
   target_sources(app PRIVATE src/behaviors/behavior_to_layer.c)
   target_sources(app PRIVATE src/behaviors/behavior_transparent.c)
   target_sources(app PRIVATE src/behaviors/behavior_none.c)
+  target_sources_ifdef(CONFIG_ZMK_BEHAVIOR_SOFT_OFF app PRIVATE src/behaviors/behavior_soft_off.c)
   target_sources_ifdef(CONFIG_ZMK_BEHAVIOR_SENSOR_ROTATE app PRIVATE src/behaviors/behavior_sensor_rotate.c)
   target_sources_ifdef(CONFIG_ZMK_BEHAVIOR_SENSOR_ROTATE_VAR app PRIVATE src/behaviors/behavior_sensor_rotate_var.c)
   target_sources_ifdef(CONFIG_ZMK_BEHAVIOR_SENSOR_ROTATE_COMMON app PRIVATE src/behaviors/behavior_sensor_rotate_common.c)

app/Kconfig.behaviors

@@ -11,6 +11,10 @@ config ZMK_BEHAVIOR_KEY_TOGGLE
     default y
     depends on DT_HAS_ZMK_BEHAVIOR_KEY_TOGGLE_ENABLED
 
+config ZMK_BEHAVIOR_SOFT_OFF
+    bool
+    default y
+    depends on DT_HAS_ZMK_BEHAVIOR_SOFT_OFF_ENABLED && ZMK_PM_SOFT_OFF
 
 config ZMK_BEHAVIOR_SENSOR_ROTATE_COMMON
     bool

app/dts/bindings/behaviors/zmk,behavior-soft-off.yaml

@@ -0,0 +1,8 @@
+# Copyright (c) 2023 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+description: Soft-Off Behavior
+
+compatible: "zmk,behavior-soft-off"
+
+include: zero_param.yaml

app/src/behaviors/behavior_soft_off.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT zmk_behavior_soft_off
+
+#include <zephyr/device.h>
+#include <drivers/behavior.h>
+#include <zephyr/logging/log.h>
+
+#include <zmk/pm.h>
+#include <zmk/behavior.h>
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#if DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT)
+
+static int behavior_soft_off_init(const struct device *dev) {
+    LOG_ERR("");
+    return 0;
+};
+
+static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
+                                     struct zmk_behavior_binding_event event) {
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static int on_keymap_binding_released(struct zmk_behavior_binding *binding,
+                                      struct zmk_behavior_binding_event event) {
+    zmk_pm_soft_off();
+
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static const struct behavior_driver_api behavior_soft_off_driver_api = {
+    .binding_pressed = on_keymap_binding_pressed,
+    .binding_released = on_keymap_binding_released,
+};
+
+DEVICE_DT_INST_DEFINE(0, behavior_soft_off_init, NULL, NULL, NULL, APPLICATION,
+                      CONFIG_KERNEL_INIT_PRIORITY_DEFAULT, &behavior_soft_off_driver_api);
+
+#endif /* DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT) */