iio: adc: ad4695: Add driver for AD4695 and similar ADCs

This is a new driver for Analog Devices Inc. AD4695 and similar ADCs.
The initial driver supports initializing the chip including configuring
all possible LDO and reference voltage sources as well as any possible
voltage input channel wiring configuration.

Only the 4-wire SPI wiring mode where the CNV pin is tied to the CS pin
is supported at this time. And reading sample data from the ADC can only
be done in direct mode for now.

Co-developed-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240711-iio-adc-ad4695-v4-2-c31621113b57@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/adc/Kconfig

@@ -73,6 +73,17 @@ config AD4630
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad4630.
 
+config AD4695
+	tristate "Analog Device AD4695 ADC Driver"
+	depends on SPI
+	select REGMAP_SPI
+	help
+	  Say yes here to build support for Analog Devices AD4695 and similar
+	  analog to digital converters (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad4695.
+
 config AD7091R5
 	tristate "Analog Devices AD7091R5 ADC Driver"
 	depends on I2C

drivers/iio/adc/Makefile

@@ -14,6 +14,10 @@ obj-$(CONFIG_AD4630) += ad4630.o
 obj-$(CONFIG_AD6676) += ad6676.o
 obj-$(CONFIG_AD7173) += ad7173.o
 obj-$(CONFIG_AD7091R5) += ad7091r5.o ad7091r-base.o
+obj-$(CONFIG_AD4695) += ad4695.o
+obj-$(CONFIG_AD7091R) += ad7091r-base.o
+obj-$(CONFIG_AD7091R5) += ad7091r5.o
+obj-$(CONFIG_AD7091R8) += ad7091r8.o
 obj-$(CONFIG_AD7124) += ad7124.o
 obj-$(CONFIG_AD7173) += ad7173.o
 obj-$(CONFIG_AD7192) += ad7192.o