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/Documentation/devicetree/bindings/net/socfpga-dwmac.txt b/Documentation/devicetree/bindings/net/socfpga-dwmac.txt
new file mode 100644
index 0000000..636f0ac
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/socfpga-dwmac.txt
@@ -0,0 +1,27 @@
+Altera SOCFPGA SoC DWMAC controller
+
+This is a variant of the dwmac/stmmac driver an inherits all descriptions
+present in Documentation/devicetree/bindings/net/stmmac.txt.
+
+The device node has additional properties:
+
+Required properties:
+ - compatible	: Should contain "altr,socfpga-stmmac" along with
+		  "snps,dwmac" and any applicable more detailed
+		  designware version numbers documented in stmmac.txt
+ - altr,sysmgr-syscon : Should be the phandle to the system manager node that
+   encompasses the glue register, the register offset, and the register shift.
+
+Example:
+
+gmac0: ethernet@ff700000 {
+	compatible = "altr,socfpga-stmmac", "snps,dwmac-3.70a", "snps,dwmac";
+	altr,sysmgr-syscon = <&sysmgr 0x60 0>;
+	status = "disabled";
+	reg = <0xff700000 0x2000>;
+	interrupts = <0 115 4>;
+	interrupt-names = "macirq";
+	mac-address = [00 00 00 00 00 00];/* Filled in by U-Boot */
+	clocks = <&emac_0_clk>;
+	clocks-names = "stmmaceth";
+};