Add support Mercusys mr70x v2 and Tp-link ax53/55

[lleachii]

See response from a developer:

@lleachii

• What does OEM need to do if architecture/target doesn't exist
• What to do if already exists
• Why did the chip manufacturer give me this different SDK, how was it developed from OpenWrt, etc.

@daniel

Supply patches to upstream Linux kernel to add hardware support. Once hardware is supported in Linux kernel, we can add (ie. backport) support to OpenWrt.

Then it's easy, all they have to do is submit board support code (ie. device tree and board-specific user-space scripts).

Chip designers supply downstream board manufacturers with a software development kit. Usually this contains a (terribly outdated) Linux kernel and a minimal Linux user-space distribution, often times based on OpenWrt. Usually this is developed behind closed doors by the chip designer and it wouldn't even make much sense for them to send any of it upstream at the point the chip designer is working on it, as the chip is not yet mass-produced and no devices for testing/validation are available in the market.