arm: dts: rockchip: Add dts for rk3568 evb

Add dts for rk3568 evb, sync from the linux kernel
upstream list [0].

[0] https://patchwork.kernel.org/project/linux-rockchip/list/?series=474969

Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3568-evb-u-boot.dtsi b/arch/arm/dts/rk3568-evb-u-boot.dtsi
new file mode 100644
index 0000000..b03cbea
--- /dev/null
+++ b/arch/arm/dts/rk3568-evb-u-boot.dtsi
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2021 Rockchip Electronics Co., Ltd
+ */
+
+#include "rk3568-u-boot.dtsi"
+
+/ {
+	chosen {
+		stdout-path = &uart2;
+		u-boot,spl-boot-order = "same-as-spl", &sdmmc0, &sdhci;
+	};
+};
+
+&sdmmc0 {
+	status = "okay";
+};
+
+&uart2 {
+	clock-frequency = <24000000>;
+	u-boot,dm-spl;
+	status = "okay";
+};