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_arria5_socdk.dts b/arch/arm/boot/dts/socfpga_arria5_socdk.dts
index 5beffb2..a87ee1c 100644
--- a/arch/arm/boot/dts/socfpga_arria5_socdk.dts
+++ b/arch/arm/boot/dts/socfpga_arria5_socdk.dts
@@ -37,4 +37,25 @@
 		*/
 		ethernet0 = &gmac1;
 	};
+
+	aliases {
+		/* this allow the ethaddr uboot environmnet variable contents
+		 * to be added to the gmac1 device tree blob.
+		 */
+		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>;
 };