iio: at91: document ADC clock properties

Document the clock properties required by the at91 ADC driver.
Signed-off-by: Boris Brezillon <b.brezillon@overkiz.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/arm/atmel-adc.txt

@@ -5,6 +5,9 @@ Required properties:
     <chip> can be "at91sam9260", "at91sam9g45" or "at91sam9x5"
   - reg: Should contain ADC registers location and length
   - interrupts: Should contain the IRQ line for the ADC
+  - clock-names: tuple listing input clock names.
+	Required elements: "adc_clk", "adc_op_clk".
+  - clocks: phandles to input clocks.
   - atmel,adc-channels-used: Bitmask of the channels muxed and enable for this
     device
   - atmel,adc-startup-time: Startup Time of the ADC in microseconds as
@@ -44,6 +47,8 @@ adc0: adc@fffb0000 {
 	compatible = "atmel,at91sam9260-adc";
 	reg = <0xfffb0000 0x100>;
 	interrupts = <20 4>;
+	clocks = <&adc_clk>, <&adc_op_clk>;
+	clock-names = "adc_clk", "adc_op_clk";
 	atmel,adc-channel-base = <0x30>;
 	atmel,adc-channels-used = <0xff>;
 	atmel,adc-drdy-mask = <0x10000>;