ARM: dts: wheat: add QSPI support

Define the Wheat board dependent part of the QSPI device node.
Add device nodes for Spansion S25FL512S SPI flash and MTD partitions on it.

Based  on the original (and large) patch by Vladimir Barinov
<vladimir.barinov@cogentembedded.com>.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7792-wheat.dts

@@ -103,6 +103,11 @@ sdhi0_pins: sdhi0 {
 		groups = "sdhi0_data4", "sdhi0_ctrl";
 		function = "sdhi0";
 	};
+
+	qspi_pins: qspi {
+		groups = "qspi_ctrl", "qspi_data4";
+		function = "qspi";
+	};
 };
 
 &scif0 {
@@ -134,3 +139,41 @@ &sdhi0 {
 	cd-gpios = <&gpio11 11 GPIO_ACTIVE_LOW>;
 	status = "okay";
 };
+
+&qspi {
+	pinctrl-0 = <&qspi_pins>;
+	pinctrl-names = "default";
+	status = "okay";
+
+	flash@0 {
+		compatible = "spansion,s25fl512s", "jedec,spi-nor";
+		reg = <0>;
+		spi-max-frequency = <30000000>;
+		spi-tx-bus-width = <4>;
+		spi-rx-bus-width = <4>;
+		spi-cpol;
+		spi-cpha;
+		m25p,fast-read;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "loader";
+				reg = <0x00000000 0x00040000>;
+				read-only;
+			};
+			partition@40000 {
+				label = "user";
+				reg = <0x00040000 0x00400000>;
+				read-only;
+			};
+			partition@440000 {
+				label = "flash";
+				reg = <0x00440000 0x03bc0000>;
+			};
+		};
+	};
+};