board: riscv: add openpiton-riscv64 SoC support

This patch adds openpiton-riscv64 SOC support. In particular, this
board supports a standard bootflow through zsbl->u-boot SPL->
opensbi->u-boot proper->Linux. There are separate defconfigs for
building u-boot SPL and u-boot proper

Signed-off-by: Tianrui Wei <tianrui-wei@outlook.com>
Signed-off-by: Jonathan Balkind <jbalkind@ucsb.edu>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/board/openpiton/riscv64/Kconfig b/board/openpiton/riscv64/Kconfig
new file mode 100644
index 0000000..193c890
--- /dev/null
+++ b/board/openpiton/riscv64/Kconfig
@@ -0,0 +1,40 @@
+if TARGET_OPENPITON_RISCV64
+
+config SYS_BOARD
+	default "riscv64"
+
+config SYS_VENDOR
+	default "openpiton"
+
+config SYS_CPU
+	default "generic"
+
+config SYS_CONFIG_NAME
+	default "openpiton-riscv64"
+
+config SYS_TEXT_BASE
+	default 0x81000000 if SPL
+	default 0x80000000 if !RISCV_SMODE
+	default 0x81000000 if RISCV_SMODE
+
+config SPL_TEXT_BASE
+	default 0x82000000
+
+config SPL_OPENSBI_LOAD_ADDR
+	default 0x80000000
+
+config BOARD_SPECIFIC_OPTIONS # dummy
+	def_bool y
+	select ARCH_EARLY_INIT_R
+	select SUPPORT_SPL
+	imply CPU_RISCV
+	imply RISCV_TIMER
+	imply SPL_SIFIVE_CLINT
+	imply CMD_CPU
+	imply SPL_CPU_SUPPORT
+	imply SPL_SMP
+	imply SPL_MMC
+	imply SMP
+	imply SPL_RISCV_MMODE
+
+endif