drivers/rtc/rtc-pcf2123.c: add support for devicetree

Add compatible string "nxp,rtc-pcf2123"
Document the binding

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/devicetree/bindings/rtc/nxp,rtc-2123.txt

@@ -0,0 +1,16 @@
+NXP PCF2123 SPI Real Time Clock
+
+Required properties:
+- compatible: should be: "nxp,rtc-pcf2123"
+- reg: should be the SPI slave chipselect address
+
+Optional properties:
+- spi-cs-high: PCF2123 needs chipselect high
+
+Example:
+
+rtc: nxp,rtc-pcf2123@3 {
+	compatible = "nxp,rtc-pcf2123"
+	reg = <3>
+	spi-cs-high;
+};

drivers/rtc/rtc-pcf2123.c

@@ -38,6 +38,7 @@
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/of.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/rtc.h>
@@ -340,10 +341,19 @@ static int pcf2123_remove(struct spi_device *spi)
 	return 0;
 }
 
+#ifdef CONFIG_OF
+static const struct of_device_id pcf2123_dt_ids[] = {
+	{ .compatible = "nxp,rtc-pcf2123", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pcf2123_dt_ids);
+#endif
+
 static struct spi_driver pcf2123_driver = {
 	.driver	= {
 			.name	= "rtc-pcf2123",
 			.owner	= THIS_MODULE,
+			.of_match_table = of_match_ptr(pcf2123_dt_ids),
 	},
 	.probe	= pcf2123_probe,
 	.remove	= pcf2123_remove,