mb/intel/mtlrvp: Add configuration for UART devices

This patch adds below configuration for MTL-RVP UART devices,
Interface -> UART0
PCI -> 0:0x1e:0
Device -> AP UART

BUG=b:224325352
TEST=Able to build with the patch and boot the mtlrvp ito chromeOS
using subsequent patches in the train. UART logs appear on AP console.

Signed-off-by: Harsha B R <harsha.b.r@intel.com>
Change-Id: I4702d603aa49357f4db0d18d646e536d9d81787e
Signed-off-by: Jamie Ryu <jamie.m.ryu@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70873
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Krishna P Bhat D <krishna.p.bhat.d@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/mainboard/intel/mtlrvp/Kconfig

@@ -22,6 +22,10 @@ config CHROMEOS
 	select GBB_FLAG_DISABLE_PD_SOFTWARE_SYNC
 	select HAS_RECOVERY_MRC_CACHE
 
+config BOARD_SPECIFIC_OPTIONS
+	def_bool y
+	select INTEL_LPSS_UART_FOR_CONSOLE
+
 config MAINBOARD_DIR
 	default "intel/mtlrvp"
 
@@ -81,4 +85,8 @@ endchoice
 config VBOOT
 	select VBOOT_LID_SWITCH
 
+config UART_FOR_CONSOLE
+	int
+	default 0
+
 endif # BOARD_INTEL_MTLRVP_COMMON

src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb

@@ -11,6 +11,12 @@ chip soc/intel/meteorlake
 	# EC memory map range is 0x900-0x9ff
 	register "gen3_dec" = "0x00fc0901"
 
+	register "serial_io_uart_mode" = "{
+		[PchSerialIoIndexUART0] = PchSerialIoPci,
+		[PchSerialIoIndexUART1] = PchSerialIoDisabled,
+		[PchSerialIoIndexUART2] = PchSerialIoDisabled,
+	}"
+
 	device domain 0 on
 		device ref igpu on end
 		device ref heci1 on end