mmc: dw_mmc: add device tree support

Add device tree based discovery support.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

Documentation/devicetree/bindings/mmc/synposis-dw-mshc.txt

@@ -0,0 +1,79 @@
+* Synopsis Designware Mobile Storage Host Controller
+
+The Synopsis 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 mmc properties described by mmc.txt and the
+properties used by the Synopsis Designware Mobile Storage Host Controller.
+
+Required Properties:
+
+* compatible: should be
+	- snps,dw-mshc: for controllers compliant with synopsis dw-mshc.
+* #address-cells: should be 1.
+* #size-cells: should be 0.
+
+# Slots: The slot specific information are contained within child-nodes with
+  each child-node representing a supported slot. There should be atleast one
+  child node representing a card slot. The name of the child node representing
+  the slot is recommended to be slot@n where n is the unique number of the slot
+  connnected to the controller. The following are optional properties which
+  can be included in the slot child node.
+
+	* reg: specifies the physical slot number. The valid values of this
+	  property is 0 to (num-slots -1), where num-slots is the value
+	  specified by the num-slots property.
+
+	* bus-width: as documented in mmc core bindings.
+
+	* wp-gpios: specifies the write protect gpio line. The format of the
+	  gpio specifier depends on the gpio controller. If the write-protect
+	  line is not available, this property is optional.
+
+Optional properties:
+
+* num-slots: specifies the number of slots supported by the controller.
+  The number of physical slots actually used could be equal or less than the
+  value specified by num-slots. If this property is not specified, the value
+  of num-slot property is assumed to be 1.
+
+* fifo-depth: The maximum size of the tx/rx fifo's. If this property is not
+  specified, the default value of the fifo size is determined from the
+  controller registers.
+
+* card-detect-delay: Delay in milli-seconds before detecting card after card
+  insert event. The default value is 0.
+
+* supports-highspeed: Enables support for high speed cards (upto 50MHz)
+
+* broken-cd: as documented in mmc core bindings.
+
+Aliases:
+
+- All the MSHC controller nodes should be represented in the aliases node using
+  the following format 'mshc{n}' where n is a unique number for the alias.
+
+Example:
+
+The MSHC controller node can be split into two portions, SoC specific and
+board specific portions as listed below.
+
+	dwmmc0@12200000 {
+		compatible = "snps,dw-mshc";
+		reg = <0x12200000 0x1000>;
+		interrupts = <0 75 0>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};
+
+	dwmmc0@12200000 {
+		num-slots = <1>;
+		supports-highspeed;
+		broken-cd;
+		fifo-depth = <0x80>;
+		card-detect-delay = <200>;
+
+		slot@0 {
+			reg = <0>;
+			bus-width = <8>;
+		};
+	};