iio: add APDS9300 ambilent light sensor driver

This patch adds IIO driver for APDS9300 ambient light sensor (ALS).
http://www.avagotech.com/docs/AV02-1077EN

The driver allows to read raw data from ADC registers or calculate
lux value. It also can handle threshold interrupt.
Signed-off-by: Oleksandr Kravchenko <o.v.kravchenko@globallogic.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/light/apds9300.txt

+* Avago APDS9300 ambient light sensor
+
+http://www.avagotech.com/docs/AV02-1077EN
+
+Required properties:
+
+  - compatible : should be "avago,apds9300"
+  - reg : the I2C address of the sensor
+
+Optional properties:
+
+  - interrupt-parent : should be the phandle for the interrupt controller
+  - interrupts : interrupt mapping for GPIO IRQ
+
+Example:
+
+apds9300@39 {
+	compatible = "avago,apds9300";
+	reg = <0x39>;
+	interrupt-parent = <&gpio2>;
+	interrupts = <29 8>;
+};

drivers/iio/light/Kconfig

@@ -17,6 +17,16 @@ config ADJD_S311
 	 This driver can also be built as a module.  If so, the module
 	 will be called adjd_s311.
 
+config APDS9300
+	tristate "APDS9300 ambient light sensor"
+	depends on I2C
+	help
+	 Say Y here if you want to build a driver for the Avago APDS9300
+	 ambient light sensor.
+
+	 To compile this driver as a module, choose M here: the
+	 module will be called apds9300.
+
 config HID_SENSOR_ALS
 	depends on HID_SENSOR_HUB
 	select IIO_BUFFER

drivers/iio/light/Makefile

@@ -4,6 +4,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
+obj-$(CONFIG_APDS9300)		+= apds9300.o
 obj-$(CONFIG_HID_SENSOR_ALS)	+= hid-sensor-als.o
 obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o
 obj-$(CONFIG_SENSORS_TSL2563)	+= tsl2563.o