mips: mtmips: add support for MediaTek MT7620 SoC

This patch adds support for MediaTek MT7620 SoC.
All files are dedicated for u-boot.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
diff --git a/arch/mips/mach-mtmips/Kconfig b/arch/mips/mach-mtmips/Kconfig
index c383e82..8756cadb 100644
--- a/arch/mips/mach-mtmips/Kconfig
+++ b/arch/mips/mach-mtmips/Kconfig
@@ -5,6 +5,7 @@
 	default 0x1000
 
 config SYS_SOC
+	default "mt7620" if SOC_MT7620
 	default "mt7628" if SOC_MT7628
 
 config SYS_DCACHE_SIZE
@@ -31,10 +32,26 @@
 
 config BUILD_TARGET
 	default "u-boot-with-spl.bin" if SPL
+	default "u-boot.bin"
 
 choice
 	prompt "MediaTek MIPS SoC select"
 
+config SOC_MT7620
+	bool "MT7620"
+	select MIPS_L1_CACHE_SHIFT_5
+	select SYS_MIPS_CACHE_INIT_RAM_LOAD
+	select PINCTRL_MT7620
+	select MT7620_SERIAL
+	select MISC
+	select SPL_SEPARATE_BSS if SPL
+	select SPL_LOADER_SUPPORT if SPL
+	select SPL_OF_CONTROL if SPL_DM
+	select SPL_OF_PLATDATA if SPL_DM
+	select SPL_DM_SERIAL if SPL_DM
+	help
+	  This supports MediaTek MT7620.
+
 config SOC_MT7628
 	bool "MT7628"
 	select MIPS_L1_CACHE_SHIFT_5
@@ -59,6 +76,7 @@
 
 endchoice
 
+source "arch/mips/mach-mtmips/mt7620/Kconfig"
 source "arch/mips/mach-mtmips/mt7628/Kconfig"
 
 endmenu