rtc: mcp795: add devicetree support

Add device tree support to the rtc-mcp795 driver.
Signed-off-by: Emil Bartczak <emilbart@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

Documentation/devicetree/bindings/rtc/maxim,mcp795.txt

+* Maxim MCP795		SPI Serial Real-Time Clock
+
+Required properties:
+- compatible: Should contain "maxim,mcp795".
+- reg: SPI address for chip
+
+Example:
+	mcp795: rtc@0 {
+		compatible = "maxim,mcp795";
+		reg = <0>;
+	};

drivers/rtc/rtc-mcp795.c

@@ -20,6 +20,7 @@
 #include <linux/printk.h>
 #include <linux/spi/spi.h>
 #include <linux/rtc.h>
+#include <linux/of.h>
 
 /* MCP795 Instructions, see datasheet table 3-1 */
 #define MCP795_EEREAD	0x03
@@ -183,9 +184,18 @@ static int mcp795_probe(struct spi_device *spi)
 	return 0;
 }
 
+#ifdef CONFIG_OF
+static const struct of_device_id mcp795_of_match[] = {
+	{ .compatible = "maxim,mcp795" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mcp795_of_match);
+#endif
+
 static struct spi_driver mcp795_driver = {
 		.driver = {
 				.name = "rtc-mcp795",
+				.of_match_table = of_match_ptr(mcp795_of_match),
 		},
 		.probe = mcp795_probe,
 };