board: rockchip: Add rk3308 evb support

Add support for rk3308 evaluation board.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

board/rockchip/evb_rk3308/Kconfig

@@ -0,0 +1,15 @@
+if TARGET_EVB_RK3308
+
+config SYS_BOARD
+	default "evb_rk3308"
+
+config SYS_VENDOR
+	default "rockchip"
+
+config SYS_CONFIG_NAME
+	default "evb_rk3308"
+
+config BOARD_SPECIFIC_OPTIONS # dummy
+	def_bool y
+
+endif

board/rockchip/evb_rk3308/MAINTAINERS

@@ -0,0 +1,6 @@
+EVB-RK3308
+M:      Andy Yan <andy.yan@rock-chips.com>
+S:      Maintained
+F:      board/rockchip/evb_rk3308
+F:      include/configs/evb_rk3308.h
+F:      configs/evb-rk3308_defconfig

board/rockchip/evb_rk3308/Makefile

@@ -0,0 +1,7 @@
+#
+# (C) Copyright 2018 Rockchip Electronics Co., Ltd
+#
+# SPDX-License-Identifier:     GPL-2.0+
+#
+
+obj-y	+= evb_rk3308.o

board/rockchip/evb_rk3308/evb_rk3308.c

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2018 Rockchip Electronics Co., Ltd
+ */
+
+#include <common.h>
+#include <adc.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define KEY_DOWN_MIN_VAL        0
+#define KEY_DOWN_MAX_VAL        30
+
+/*
+ * Two board variants whith adc channel 3 is for board id
+ * v10: 1024, v11: 512
+ * v10: adc channel 0 for dnl key
+ * v11: adc channel 1 for dnl key
+ */
+int rockchip_dnl_key_pressed(void)
+{
+	unsigned int key_val, id_val;
+	int key_ch;
+
+	if (adc_channel_single_shot("saradc", 3, &id_val)) {
+		printf("%s read board id failed\n", __func__);
+		return false;
+	}
+
+	if (abs(id_val - 1024) <= 30)
+		key_ch = 0;
+	else
+		key_ch = 1;
+
+	if (adc_channel_single_shot("saradc", key_ch, &key_val)) {
+		printf("%s read adc key val failed\n", __func__);
+		return false;
+	}
+
+	if (key_val >= KEY_DOWN_MIN_VAL && key_val <= KEY_DOWN_MAX_VAL)
+		return true;
+	else
+		return false;
+}