usb: phy: samsung: Add support to set pmu isolation

Adding support to parse device node data in order to get
required properties to set pmu isolation for usb-phy.

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Documentation/devicetree/bindings/usb/samsung-usbphy.txt

@@ -9,3 +9,39 @@ Required properties:
 - compatible : should be "samsung,exynos4210-usbphy"
 - reg : base physical address of the phy registers and length of memory mapped
 	region.
+
+Optional properties:
+- #address-cells: should be '1' when usbphy node has a child node with 'reg'
+		  property.
+- #size-cells: should be '1' when usbphy node has a child node with 'reg'
+	       property.
+- ranges: allows valid translation between child's address space and parent's
+	  address space.
+
+- The child node 'usbphy-sys' to the node 'usbphy' is for the system controller
+  interface for usb-phy. It should provide the following information required by
+  usb-phy controller to control phy.
+  - reg : base physical address of PHY_CONTROL registers.
+	  The size of this register is the total sum of size of all PHY_CONTROL
+	  registers that the SoC has. For example, the size will be
+	  '0x4' in case we have only one PHY_CONTROL register (e.g.
+	  OTHERS register in S3C64XX or USB_PHY_CONTROL register in S5PV210)
+	  and, '0x8' in case we have two PHY_CONTROL registers (e.g.
+	  USBDEVICE_PHY_CONTROL and USBHOST_PHY_CONTROL registers in exynos4x).
+	  and so on.
+
+Example:
+ - Exynos4210
+
+	usbphy@125B0000 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "samsung,exynos4210-usbphy";
+		reg = <0x125B0000 0x100>;
+		ranges;
+
+		usbphy-sys {
+			/* USB device and host PHY_CONTROL registers */
+			reg = <0x10020704 0x8>;
+		};
+	};