rtc: rtc-s3c: Add device tree support

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

Cc: Ben Dooks <[e-mail]>
Signed-off-by: Thomas Abraham <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
Signed-off-by: Kukjin Kim <[e-mail]>

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

···
+* 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>;
+	};

drivers/rtc/rtc-s3c.c

···
 #include <linux/clk.h>
 #include <linux/log2.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 
 #include <mach/hardware.h>
 #include <asm/uaccess.h>
···
 		goto err_nortc;
 	}
 
-	s3c_rtc_cpu_type = platform_get_device_id(pdev)->driver_data;
+#ifdef CONFIG_OF
+	if (pdev->dev.of_node)
+		s3c_rtc_cpu_type = of_device_is_compatible(pdev->dev.of_node,
+			"samsung,s3c6410-rtc") ? TYPE_S3C64XX : TYPE_S3C2410;
+	else
+#endif
+		s3c_rtc_cpu_type = platform_get_device_id(pdev)->driver_data;
 
 	/* Check RTC Time */
 
···
 #define s3c_rtc_resume  NULL
 #endif
 
+#ifdef CONFIG_OF
+static const struct of_device_id s3c_rtc_dt_match[] = {
+	{ .compatible = "samsung,s3c2410-rtc" },
+	{ .compatible = "samsung,s3c6410-rtc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, s3c_rtc_dt_match);
+#else
+#define s3c_rtc_dt_match NULL
+#endif
+
 static struct platform_device_id s3c_rtc_driver_ids[] = {
 	{
 		.name		= "s3c2410-rtc",
···
 	.driver		= {
 		.name	= "s3c-rtc",
 		.owner	= THIS_MODULE,
+		.of_match_table	= s3c_rtc_dt_match,
 	},
 };