drivers/rtc/rtc-isl12022.c: device tree support

Add support for configuring the ISL12022 real-time clock via the Device
tree framework. This is based on what I've seen in the related ISL12057
driver, it has been tested and works on a Technologic Systems TS-7670
device which uses a ISL12020 RTC device, my device tree looks like this:

apbx@80040000 {
i2c0: i2c@80058000 {
pinctrl-names = "default";
pinctrl-0 = <&i2c0_pins_a>;
clock-frequency = <400000>;
status = "okay";

isl12022@0x6f {
compatible = "isl,isl12022";
reg = <0x6f>;
};
};
... etc
};

Signed-off-by: Stuart Longland <[e-mail]>
Cc: Roman Fietze <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-isl12022.c

···
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 
 #define DRV_VERSION "0.1"
 
···
 	return PTR_ERR_OR_ZERO(isl12022->rtc);
 }
 
+#ifdef CONFIG_OF
+static struct of_device_id isl12022_dt_match[] = {
+	{ .compatible = "isl,isl12022" },
+	{ },
+};
+#endif
+
 static const struct i2c_device_id isl12022_id[] = {
 	{ "isl12022", 0 },
 	{ }
···
 static struct i2c_driver isl12022_driver = {
 	.driver		= {
 		.name	= "rtc-isl12022",
+#ifdef CONFIG_OF
+		.of_match_table = of_match_ptr(isl12022_dt_match),
+#endif
 	},
 	.probe		= isl12022_probe,
 	.id_table	= isl12022_id,