[Core] Allow usage of ChibiOS's SIO driver for split keyboards

[KarlK90]

This PR build upon #16647 while this one is not merged please ignore the commit Use a mutex for split shared memory synchronization in this PR.

Description

Allow usage of 21.11+ ChibiOS's SIO driver for split keyboards. The cool thing about the SERIAL and SIO driver is that both implement the BaseChannel interface that provides blocking reading and writing methods that resemble what we already use in the driver. Only some low level aspects like initialization have to be handled differently.

Supported Hardware (incomplete)

Every STM32 MCU family that supports USARTv2 or USARTv3 like:

• STM32F0xx (Patches needed to enable SIO IRQ handler)
• STM32F3xx (Patches needed to enable SIO IRQ handler)
• STM32G0xx
• STM32G4xx
• RP2040

For test-driving these changes do the following:

1. Add these configs to your keyboard:

config.h

#define SERIAL_USART_DRIVER SIOD3 // Or whatever your usart peripheral is

halconf.h

#define HAL_USE_SIO TRUE

mcuconf.h

#define STM32_IRQ_USART3_PRIORITY 12
#define STM32_SIO_USE_USART3 TRUE // Or what ever you usart peripheral is

Target use-case is the RP2040 which only implements this driver at this point.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Split support for RP2040 [Core] Add Raspberry Pi RP2040 support #14877

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[KarlK90]

Updated the docs, this is now ready to be reviewed.

[KarlK90]

@daskygit as you use G4s on a crkbd could you help verifying that the SIO driver works as expected in Half-duplex? 🙂

[daskygit]

After some troubleshooting on Discord with Karl it's working well.