arm64: dts: renesas: cat875: Add ethernet support

This patch adds ethernet support to the sub board.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/cat875.dtsi

@@ -7,4 +7,34 @@
 
 / {
 	model = "Silicon Linux sub board for CAT874 (CAT875)";
+
+	aliases {
+		ethernet0 = &avb;
+	};
+};
+
+&avb {
+	pinctrl-0 = <&avb_pins>;
+	pinctrl-names = "default";
+	renesas,no-ether-link;
+	phy-handle = <&phy0>;
+	phy-mode = "rgmii";
+	status = "okay";
+
+	phy0: ethernet-phy@0 {
+		rxc-skew-ps = <1500>;
+		reg = <0>;
+		interrupt-parent = <&gpio2>;
+		interrupts = <21 IRQ_TYPE_LEVEL_LOW>;
+		reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
+	};
+};
+
+&pfc {
+	avb_pins: avb {
+		mux {
+			groups = "avb_mii";
+			function = "avb";
+		};
+	};
 };