drivers: serial: Added support for PIO based UART

Added a full(ish) PIO based uart driver.

Supports [5, 6, 7, 8]N[0.5, 1, 1.5, 2] modes.

Experiments were made with adding parity support on the TX side,
and wide (9 bit) data support. However I don't think these are really
usefull ATM.

Supports interrupt driven mode and polled mode. Can be used as
a shell uart.

Uses 2 state machines and < 16 instruction, therefore, 4 extra
uarts could be added to the pico.

Signed-off-by: TOKITA Hiroshi <[email protected]>
Signed-off-by: Yonatan Schachter <[email protected]>
Signed-off-by: Ionut Catalin Pavel <[email protected]>

Author: iocapa

boards/arm/rpi_pico/doc/index.rst

@@ -83,7 +83,7 @@ hardware features:
      - :dtcompatible:`raspberrypi,pico-flash`
    * - UART (PIO)
      - :kconfig:option:`CONFIG_SERIAL`
-     - :dtcompatible:`raspberrypi,pico-uart-pio`
+     - :dtcompatible:`raspberrypi,pico-pio-uart`
 
 Pin Mapping
 ===========

drivers/serial/Kconfig.rpi_pico

@@ -15,6 +15,5 @@ config UART_RPI_PICO_PIO
 	default y
 	depends on DT_HAS_RASPBERRYPI_PICO_UART_PIO_ENABLED
 	select SERIAL_HAS_DRIVER
-	select PICOSDK_USE_PIO
-	select PICOSDK_USE_CLAIM
+	select SERIAL_SUPPORT_INTERRUPT
 	depends on RESET