iio: adc: rockchip_saradc: add saradc support for rk3399

The ADC is a 6-channel signal-ended 10-bit Successive
Approximation Register (SAR) A/D Converter.
Signed-off-by: David Wu <david.wu@rock-chips.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/adc/rockchip-saradc.txt

 Rockchip Successive Approximation Register (SAR) A/D Converter bindings
 
 Required properties:
-- compatible: Should be "rockchip,saradc" or "rockchip,rk3066-tsadc"
+- compatible: should be "rockchip,<name>-saradc" or "rockchip,rk3066-tsadc"
+   - "rockchip,saradc": for rk3188, rk3288
+   - "rockchip,rk3066-tsadc": for rk3036
+   - "rockchip,rk3399-saradc": for rk3399
+
 - reg: physical base address of the controller and length of memory mapped
        region.
 - interrupts: The interrupt number to the cpu. The interrupt specifier format

drivers/iio/adc/rockchip_saradc.c

@@ -159,6 +159,22 @@ static const struct rockchip_saradc_data rk3066_tsadc_data = {
 	.clk_rate = 50000,
 };
 
+static const struct iio_chan_spec rockchip_rk3399_saradc_iio_channels[] = {
+	ADC_CHANNEL(0, "adc0"),
+	ADC_CHANNEL(1, "adc1"),
+	ADC_CHANNEL(2, "adc2"),
+	ADC_CHANNEL(3, "adc3"),
+	ADC_CHANNEL(4, "adc4"),
+	ADC_CHANNEL(5, "adc5"),
+};
+
+static const struct rockchip_saradc_data rk3399_saradc_data = {
+	.num_bits = 10,
+	.channels = rockchip_rk3399_saradc_iio_channels,
+	.num_channels = ARRAY_SIZE(rockchip_rk3399_saradc_iio_channels),
+	.clk_rate = 1000000,
+};
+
 static const struct of_device_id rockchip_saradc_match[] = {
 	{
 		.compatible = "rockchip,saradc",
@@ -166,6 +182,9 @@ static const struct of_device_id rockchip_saradc_match[] = {
 	}, {
 		.compatible = "rockchip,rk3066-tsadc",
 		.data = &rk3066_tsadc_data,
+	}, {
+		.compatible = "rockchip,rk3399-saradc",
+		.data = &rk3399_saradc_data,
 	},
 	{},
 };