serial: stm32-usart: Add STM32 USART Driver

This drivers adds support to the STM32 USART controller, which is a
standard serial driver.

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1608,6 +1608,23 @@ config SERIAL_SPRD_CONSOLE
 	  with "earlycon" on the kernel command line. The console is
 	  enabled when early_param is processed.
 
+config SERIAL_STM32
+	tristate "STMicroelectronics STM32 serial port support"
+	select SERIAL_CORE
+	depends on ARM || COMPILE_TEST
+	help
+	  This driver is for the on-chip Serial Controller on
+	  STMicroelectronics STM32 MCUs.
+	  USART supports Rx & Tx functionality.
+	  It support all industry standard baud rates.
+
+	  If unsure, say N.
+
+config SERIAL_STM32_CONSOLE
+	bool "Support for console on STM32"
+	depends on SERIAL_STM32=y
+	select SERIAL_CORE_CONSOLE
+
 endmenu
 
 config SERIAL_MCTRL_GPIO