drivers/tty/serial: add ESP32S3 ACM gadget driver

Add driver for the ACM gadget controller of the Espressif ESP32S3 SoC.
Hardware specification is available at the following URL:

  https://www.espressif.com/sites/default/files/documentation/esp32-s3_technical_reference_manual_en.pdf
  (Chapter 33 USB Serial/JTAG Controller)

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/r/20231010085926.1021667-6-jcmvbkbc@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1591,6 +1591,19 @@ config SERIAL_ESP32
 	    earlycon=esp32s3uart,mmio32,0x60000000,115200n8,40000000
 	    earlycon=esp32uart,mmio32,0x3ff40000,115200n8
 
+config SERIAL_ESP32_ACM
+	tristate "Espressif ESP32 USB ACM gadget support"
+	depends on XTENSA_PLATFORM_ESP32 || (COMPILE_TEST && OF)
+	select SERIAL_CORE
+	select SERIAL_CORE_CONSOLE
+	select SERIAL_EARLYCON
+	help
+	  Driver for the CDC ACM gadget controller of the Espressif ESP32S3
+	  SoCs that share separate USB controller with the JTAG adapter.
+	  When earlycon option is enabled the following kernel command line
+	  snippet may be used:
+	    earlycon=esp32s3acm,mmio32,0x60038000
+
 endmenu
 
 config SERIAL_MCTRL_GPIO

drivers/tty/serial/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_SERIAL_CPM)		+= cpm_uart.o
 obj-$(CONFIG_SERIAL_CONEXANT_DIGICOLOR)	+= digicolor-usart.o
 obj-$(CONFIG_SERIAL_DZ)			+= dz.o
 obj-$(CONFIG_SERIAL_ESP32)		+= esp32_uart.o
+obj-$(CONFIG_SERIAL_ESP32_ACM)		+= esp32_acm.o
 obj-$(CONFIG_SERIAL_FSL_LINFLEXUART)	+= fsl_linflexuart.o
 obj-$(CONFIG_SERIAL_FSL_LPUART)		+= fsl_lpuart.o
 obj-$(CONFIG_SERIAL_ICOM)		+= icom.o