mb/intel/mtlrvp: Add initial code for mtlrvp_p_ext_ec variant board

This patch adds the initial code for mtlrvp_p_ext_ec variant board
which includes
1. support for 2 mainboards (Chrome EC and Windows EC) by
adding overridetree.cb to corresponding directory
2. Move devicetree to baseboard/mtlrvp_p
3. Update mainboard name in Kconfig and Kconfig.name
4. Add config option to select corresponding overridetree.cb

Subsequent patches include patch train starting from (CB - 66102)

BUG=b:260654043
TEST=Able to build with the patch and boot the mtlrvp platform with the
subsequent patches

Signed-off-by: Harsha B R <harsha.b.r@intel.com>
Change-Id: I83948aa5e9fcaadee4745e313360773c48142f89
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70346
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Usha P <usha.p@intel.com>

src/mainboard/intel/mtlrvp/Kconfig

@@ -8,6 +8,9 @@ config BOARD_INTEL_MTLRVP_COMMON
 config BOARD_INTEL_MTLRVP_P
 	select BOARD_INTEL_MTLRVP_COMMON
 
+config BOARD_INTEL_MTLRVP_P_EXT_EC
+	select BOARD_INTEL_MTLRVP_COMMON
+
 if BOARD_INTEL_MTLRVP_COMMON
 
 config MAINBOARD_DIR
@@ -15,7 +18,7 @@ config MAINBOARD_DIR
 
 config BASEBOARD_DIR
 	string
-	default "mtlrvp"
+	default "mtlrvp_p" if BOARD_INTEL_MTLRVP_P || BOARD_INTEL_MTLRVP_P_EXT_EC
 
 config MAINBOARD_PART_NUMBER
 	string
@@ -31,9 +34,14 @@ config MAINBOARD_FAMILY
 config VARIANT_DIR
 	string
 	default "mtlrvp_p" if BOARD_INTEL_MTLRVP_P
+	default "mtlrvp_p_ext_ec" if BOARD_INTEL_MTLRVP_P_EXT_EC
 
 config DEVICETREE
 	string
-	default "devicetree.cb"
+	default "variants/baseboard/\$(CONFIG_BASEBOARD_DIR)/devicetree.cb"
+
+config OVERRIDE_DEVICETREE
+	string
+	default "variants/\$(CONFIG_VARIANT_DIR)/overridetree.cb"
 
 endif # BOARD_INTEL_MTLRVP_COMMON

src/mainboard/intel/mtlrvp/Kconfig.name

@@ -1,2 +1,5 @@
 config BOARD_INTEL_MTLRVP_P
 	bool "Meteorlake-P RVP"
+
+config BOARD_INTEL_MTLRVP_P_EXT_EC
+	bool "Meteorlake-P RVP with Chrome EC"

src/mainboard/intel/mtlrvp/variants/mtlrvp_p/overridetree.cb

@@ -0,0 +1,4 @@
+chip soc/intel/meteorlake
+
+	device domain 0 on end
+end

src/mainboard/intel/mtlrvp/variants/mtlrvp_p_ext_ec/overridetree.cb

@@ -0,0 +1,4 @@
+chip soc/intel/meteorlake
+
+	device domain 0 on end
+end