dts: socfpga: Add DTS entry for adding the stmmac glue layer for stmmac.

This patch adds the dts bindings documenation for the Altera SOCFPGA glue
layer for the Synopsys STMMAC ethernet driver.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm/boot/dts/socfpga_cyclone5_socdk.dts b/arch/arm/boot/dts/socfpga_cyclone5_socdk.dts
index 2ee52ab..ae16d97 100644
--- a/arch/arm/boot/dts/socfpga_cyclone5_socdk.dts
+++ b/arch/arm/boot/dts/socfpga_cyclone5_socdk.dts
@@ -38,3 +38,17 @@
 		ethernet0 = &gmac1;
 	};
 };
+
+&gmac1 {
+	status = "okay";
+	phy-mode = "rgmii";
+
+	rxd0-skew-ps = <0>;
+	rxd1-skew-ps = <0>;
+	rxd2-skew-ps = <0>;
+	rxd3-skew-ps = <0>;
+	txen-skew-ps = <0>;
+	txc-skew-ps = <2600>;
+	rxdv-skew-ps = <0>;
+	rxc-skew-ps = <2000>;
+};