rtc: rtc-s3c: Add device tree support

Add device tree based discovery support for Samsung's rtc controller.

Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

Documentation/devicetree/bindings/rtc/s3c-rtc.txt

@@ -0,0 +1,20 @@
+* Samsung's S3C Real Time Clock controller
+
+Required properties:
+- compatible: should be one of the following.
+    * "samsung,s3c2410-rtc" - for controllers compatible with s3c2410 rtc.
+    * "samsung,s3c6410-rtc" - for controllers compatible with s3c6410 rtc.
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- interrupts: Two interrupt numbers to the cpu should be specified. First
+  interrupt number is the rtc alarm interupt and second interrupt number
+  is the rtc tick interrupt. The number of cells representing a interrupt
+  depends on the parent interrupt controller.
+
+Example:
+
+	rtc@10070000 {
+		compatible = "samsung,s3c6410-rtc";
+		reg = <0x10070000 0x100>;
+		interrupts = <44 0 45 0>;
+	};