dts: socfpga: Add support for SD/MMC on the SOCFPGA platform

Introduce "altr,socfpga-dw-mshc" to enable Altera's SOCFPGA platform
specific implementation of the dw_mmc driver.

Also add the "syscon" binding to the "altr,sys-mgr" node. The clock
driver can use the syscon driver to toggle the register for the SD/MMC
clock phase shift settings.

Finally, fix an indentation error for the sysmgr node.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Acked-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Chris Ball <chris@printf.net>
diff --git a/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt
new file mode 100644
index 0000000..4897bea
--- /dev/null
+++ b/Documentation/devicetree/bindings/mmc/socfpga-dw-mshc.txt
@@ -0,0 +1,23 @@
+* Altera SOCFPGA specific extensions to the Synopsys Designware Mobile
+  Storage Host Controller
+
+The Synopsys designware mobile storage host controller is used to interface
+a SoC with storage medium such as eMMC or SD/MMC cards. This file documents
+differences between the core Synopsys dw mshc controller properties described
+by synopsys-dw-mshc.txt and the properties used by the Altera SOCFPGA specific
+extensions to the Synopsys Designware Mobile Storage Host Controller.
+
+Required Properties:
+
+* compatible: should be
+	- "altr,socfpga-dw-mshc": for Altera's SOCFPGA platform
+
+Example:
+
+	mmc: dwmmc0@ff704000 {
+		compatible = "altr,socfpga-dw-mshc";
+		reg = <0xff704000 0x1000>;
+		interrupts = <0 129 4>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};