arm64: dts: renesas: gray-hawk-single: Add QSPI FLASH support

Describe the QSPI FLASH on the Gray Hawk Single board.
Signed-off-by: Cong Dang <cong.dang.xn@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/96d6567024cef9fcd6b04f92a697301c1c8d1d8e.1708354463.git.geert+renesas@glider.be

arch/arm64/boot/dts/renesas/r8a779h0-gray-hawk-single.dts

@@ -181,12 +181,45 @@ mmc_pins: mmc {
 		power-source = <1800>;
 	};
 
+	qspi0_pins: qspi0 {
+		groups = "qspi0_ctrl", "qspi0_data4";
+		function = "qspi0";
+	};
+
 	scif_clk_pins: scif-clk {
 		groups = "scif_clk";
 		function = "scif_clk";
 	};
 };
 
+&rpc {
+	pinctrl-0 = <&qspi0_pins>;
+	pinctrl-names = "default";
+
+	status = "okay";
+
+	flash@0 {
+		compatible = "spansion,s25fs512s", "jedec,spi-nor";
+		reg = <0>;
+		spi-max-frequency = <40000000>;
+		spi-rx-bus-width = <4>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			boot@0 {
+				reg = <0x0 0x1200000>;
+				read-only;
+			};
+			user@1200000 {
+				reg = <0x1200000 0x2e00000>;
+			};
+		};
+	};
+};
+
 &rwdt {
 	timeout-sec = <60>;
 	status = "okay";