iio: adc: add driver for Rockchip saradc

The ADC is a 3-channel signal-ended 10-bit Successive Approximation
Register (SAR) A/D Converter. It uses the supply and ground as its reference
and converts the analog input signal into 10-bit binary digital codes.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 3ea56a3..6655fd4 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -206,6 +206,16 @@
 	  To compile this driver as a module, choose M here: the
 	  module will be called nau7802.
 
+config ROCKCHIP_SARADC
+	tristate "Rockchip SARADC driver"
+	depends on ARCH_ROCKCHIP || (ARM && COMPILE_TEST)
+	help
+	  Say yes here to build support for the SARADC found in SoCs from
+	  Rockchip.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called rockchip_saradc.
+
 config TI_ADC081C
 	tristate "Texas Instruments ADC081C021/027"
 	depends on I2C