Update openwrt network configs for openwrt dsa conversion

[sarcasticadmin]

Description

@davidelang caught this on the mailing list

When we upgrade to openwrt 20.0x its been suggested we update our network configurations for the onboard interfaces and switches within the AP hardware. WNDR 3700v2 and similar devices do not support dsa at this time.

This originated from the mailing list: http://lists.infradead.org/mailman/listinfo/openwrt-adm

Will get more specifics when Im fulled added to this.

Update:

• Its referred to as dsa, see: https://openwrt.org/docs/guide-user/network/dsa/converting-to-dsa

Acceptance Criteria

• Update the switch configuration for openwrt dsa conversion

[sarcasticadmin]

So attempted to take a stab at this today... Heres what I found:

The default image from the latest stable release (22.03.1) still has swconfig enabled instead of DSA for the ath79 (WNDR 3700v2, 3800, 3800ch). And support doesnt seem like something that can be enabled at this point.

Per the release notes for ~21.02.01:

However, there is no “keep-configuration” migration path from 19.07 to 21.02 for targets that [switched from 
swconfig to DSA.](https://openwrt.org/releases/21.02/notes-21.02.0#initial_dsa_support) The affected
targets are: ath79 (only TP-Link TL WR941ND), bcm4908, gemini, kirkwood, mediatek (most boards), mvebu,
octeon, ramips (mt7621 subtarget only), and realtek. Check the Target column in the table below. If your
device is listed, check its Device Page (link in the table below) or
[ask on the Forum.](https://forum.openwrt.org/)

Subsequent releases dont seem to have DSA enabled for this hardware yet

For the ath79 (WNDR 3700v2, 3800, 3800ch) architecture specifically:

DSA is not supported for the majority of the models in that architecture. As mentioned above only only TP-Link TL WR941ND

There are existing attempted to port large swaths of the architecture: openwrt/openwrt#4622 But I dont believe even this PR once merged would effect the ath79 chipset we use on for the Netgear WNDR 3700v2, 3800, & 3800ch.

The switch in the netgear WNDR 3700v2, 3800, 3800ch: Realtek RTL8366S does seem to exist in upstream with some dsa support: https://github.com/openwrt/openwrt/tree/master/target/linux/realtek/files-5.15/drivers/net/dsa/rtl83xx

Potentially it could be enabled similar to something like airoha: https://github.com/openwrt/openwrt/blob/bb2fb4f16aef574921cb75e2205b2a3c38822588/target/linux/airoha/config-5.15 by removing switchconfig:

- CONFIG_SWCONFIG=y

However I think there still need to be more done to the .dts config files releated to this board

[sarcasticadmin]

Good news is the potential front runner for #410 - https://openwrt.org/toh/linksys/e8450 has a mediatek chipset with DSA support already in master: https://github.com/openwrt/openwrt/blob/9260027535b8f7eab5481b7f545a3fc6477d14fa/target/linux/mediatek/mt7622/config-5.15#L278-L280

So what we might be able to do is just conditionally support configuration for DSA (/etc/config/network) in the single architecture until the Netgear WNDR 3700v2, 3800, 3800ch have DSA support

[sarcasticadmin]

Discussion about openwrt dsa bridge with mixed vlans:

https://forum.openwrt.org/t/migrating-to-dsa-bridging-across-vlans-not-ports/138061
https://forum.openwrt.org/t/dsa-with-two-vlan-on-one-network/111909