ARM: dts: rockchip: Add rk3588-u-boot.dtsi

Add u-boot,dm-spl and u-boot,dm-pre-reloc related properties
for Rockchip RK3588 SoC to boot the SPL.

Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3588s-u-boot.dtsi b/arch/arm/dts/rk3588s-u-boot.dtsi
new file mode 100644
index 0000000..326508d
--- /dev/null
+++ b/arch/arm/dts/rk3588s-u-boot.dtsi
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright (c) 2022 Edgeble AI Technologies Pvt. Ltd.
+ */
+
+#include "rockchip-u-boot.dtsi"
+
+/ {
+	dmc {
+		compatible = "rockchip,rk3588-dmc";
+		bootph-all;
+		status = "okay";
+	};
+
+	pmu1_grf: syscon@fd58a000 {
+		bootph-all;
+		compatible = "rockchip,rk3588-pmu1-grf", "syscon";
+		reg = <0x0 0xfd58a000 0x0 0x2000>;
+	};
+};
+
+&xin24m {
+	bootph-all;
+	status = "okay";
+};
+
+&cru {
+	bootph-pre-ram;
+	status = "okay";
+};
+
+&sys_grf {
+	bootph-pre-ram;
+	status = "okay";
+};
+
+&uart2 {
+	clock-frequency = <24000000>;
+	bootph-pre-ram;
+	status = "okay";
+};
+
+&ioc {
+	bootph-pre-ram;
+};