serial: sh-sci: Add support for RZ/T2H SCI

Define a new RSCI port type, and the RSCI 32 bits registers set.
The RZ/T2H SCI has a a fifo, and a quite different set of registers
from the original SH SCI ones.
DMA is not supported yet.

Signed-off-by: Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250630202323.279809-6-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Thierry Bultel

drivers/tty/serial/Kconfig

@@ -675,6 +675,13 @@ config SERIAL_SH_SCI_DMA
 	depends on SERIAL_SH_SCI && DMA_ENGINE
 	default ARCH_RENESAS
 
+config SERIAL_RSCI
+	tristate "Support for Renesas RZ/T2H SCI variant"
+	depends on SERIAL_SH_SCI
+	help
+	  Support for the RZ/T2H SCI variant with fifo.
+	  Say Y if you want to be able to use the RZ/T2H SCI serial port.
+
 config SERIAL_HS_LPC32XX
 	tristate "LPC32XX high speed serial port support"
 	depends on ARCH_LPC32XX || COMPILE_TEST

drivers/tty/serial/Makefile

@@ -71,6 +71,7 @@ obj-$(CONFIG_SERIAL_QCOM_GENI)		+= qcom_geni_serial.o
 obj-$(CONFIG_SERIAL_QE)			+= ucc_uart.o
 obj-$(CONFIG_SERIAL_RDA)		+= rda-uart.o
 obj-$(CONFIG_SERIAL_RP2)		+= rp2.o
+obj-$(CONFIG_SERIAL_RSCI)		+= rsci.o
 obj-$(CONFIG_SERIAL_SA1100)		+= sa1100.o
 obj-$(CONFIG_SERIAL_SAMSUNG)		+= samsung_tty.o
 obj-$(CONFIG_SERIAL_SB1250_DUART)	+= sb1250-duart.o