arm64: dts: rockchip: add rk3399 io-domain core nodes

Add the core io-domain nodes to grf and pmugrf which individual
boards than just have to enable and add the necessary supplies to.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399.dtsi

@@ -407,6 +407,11 @@ pmugrf: syscon@ff320000 {
 		reg = <0x0 0xff320000 0x0 0x1000>;
 		#address-cells = <1>;
 		#size-cells = <1>;
+
+		pmu_io_domains: io-domains {
+			compatible = "rockchip,rk3399-pmu-io-voltage-domain";
+			status = "disabled";
+		};
 	};
 
 	spi3: spi@ff350000 {
@@ -517,6 +522,11 @@ grf: syscon@ff770000 {
 		#address-cells = <1>;
 		#size-cells = <1>;
 
+		io_domains: io-domains {
+			compatible = "rockchip,rk3399-io-voltage-domain";
+			status = "disabled";
+		};
+
 		emmc_phy: phy@f780 {
 			compatible = "rockchip,rk3399-emmc-phy";
 			reg = <0xf780 0x24>;