overlays: Add w5500 overlay

Add an overlay to configure the Wiznet W5500 Ethernet controller on
SPI0. The 'cs' parameter chooses the Chip Select (default 0).

See: #3276

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

arch/arm/boot/dts/overlays/Makefile

@@ -183,6 +183,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	vga666.dtbo \
 	w1-gpio.dtbo \
 	w1-gpio-pullup.dtbo \
+	w5500.dtbo \
 	wittypi.dtbo
 
 targets += dtbs dtbs_install

arch/arm/boot/dts/overlays/README

@@ -2538,6 +2538,16 @@ Params: gpiopin                 GPIO for I/O (default "4")
         pullup                  Now enabled by default (ignored)
 
 
+Name:   w5500
+Info:   Overlay for the Wiznet W5500 Ethernet Controller on SPI0
+Load:   dtoverlay=w5500,<param>=<val>
+Params: int_pin                 GPIO used for INT (default 25)
+
+        speed                   SPI bus speed (default 30000000)
+
+        cs                      SPI bus Chip Select (default 0)
+
+
 Name:   wittypi
 Info:   Configures the wittypi RTC module.
 Load:   dtoverlay=wittypi,<param>=<val>

arch/arm/boot/dts/overlays/w5500-overlay.dts

@@ -0,0 +1,63 @@
+// Overlay for the Wiznet w5500 Ethernet Controller
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2835";
+
+	fragment@0 {
+		target = <&spidev0>;
+		__overlay__ {
+			status = "disabled";
+		};
+	};
+
+	fragment@1 {
+		target = <&spidev1>;
+		__dormant__ {
+			status = "disabled";
+		};
+	};
+
+	fragment@2 {
+		target = <&spi0>;
+		__overlay__ {
+			/* needed to avoid dtc warning */
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			status = "okay";
+
+			eth1: w5500@0{
+				compatible = "wiznet,w5500";
+				reg = <0>; /* CE0 */
+				pinctrl-names = "default";
+				pinctrl-0 = <&eth1_pins>;
+				interrupt-parent = <&gpio>;
+				interrupts = <25 0x8>;
+				spi-max-frequency = <30000000>;
+//				local-mac-address = [aa bb cc dd ee ff];
+				status = "okay";
+			};
+		};
+	};
+
+	fragment@3 {
+		target = <&gpio>;
+		__overlay__ {
+			eth1_pins: eth1_pins {
+				brcm,pins = <25>;
+				brcm,function = <0>; /* in */
+				brcm,pull = <0>; /* none */
+			};
+		};
+	};
+
+	__overrides__ {
+		int_pin = <&eth1>, "interrupts:0",
+		          <&eth1_pins>, "brcm,pins:0";
+		speed   = <&eth1>, "spi-max-frequency:0";
+		cs      = <&eth1>, "reg:0",
+			  <0>, "!0=1";
+	};
+};