dt-bindings: iio: light: add UVIS25 device bindings

Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/light/uvis25.txt

+* ST UVIS25 uv sensor
+
+Required properties:
+- compatible: should be "st,uvis25"
+- reg: i2c address of the sensor / spi cs line
+
+Optional properties:
+- interrupt-parent: should be the phandle for the interrupt controller
+- interrupts: interrupt mapping for IRQ. It should be configured with
+  flags IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_EDGE_RISING, IRQ_TYPE_LEVEL_LOW or
+  IRQ_TYPE_EDGE_FALLING.
+
+  Refer to interrupt-controller/interrupts.txt for generic interrupt
+  client node bindings.
+
+Example:
+
+uvis25@47 {
+	compatible = "st,uvis25";
+	reg = <0x47>;
+	interrupt-parent = <&gpio0>;
+	interrupts = <0 IRQ_TYPE_EDGE_RISING>;
+};