Add D1 platform (2023 edition)

[jamesmunns]

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[hawkw]

nice

[hawkw]

you love to see it!!

[hawkw]

Some nits, but this is awesome!

[jamesmunns]

@hawkw breaking this out as a longer response:

is this Lichee-RV specific, or is this UART built into the D1 SOC?

So, some of these things COULD be portable to any user of the D1, however there's a very fuzzy line today. I haven't really tackled any of the "portability challenges", like handling different configs, or pin mapping, or what DMA channel to use, or even how to handle interrupts.

These absolutely should live in the allwinner-d1/drivers crate, but the current state of the code isn't suitable for that yet. I could put it there, but it's all very hardcoded for just this one board, so far.

[hawkw]

@hawkw breaking this out as a longer response:

is this Lichee-RV specific, or is this UART built into the D1 SOC?

So, some of these things COULD be portable to any user of the D1, however there's a very fuzzy line today. I haven't really tackled any of the "portability challenges", like handling different configs, or pin mapping, or what DMA channel to use, or even how to handle interrupts.

These absolutely should live in the allwinner-d1/drivers crate, but the current state of the code isn't suitable for that yet. I could put it there, but it's all very hardcoded for just this one board, so far.

Great, thanks — I was mostly just curious about whether this could ever move to the allwinner-d1 crate. We definitely don't need to do that in this PR if it's not ready yet.