iio: adc: Add AD7768-1 ADC basic support

The ad7768-1 is a single channel, precision 24-bit analog to digital
converter (ADC).

This basic patch configures the device in fast mode, with 32 kSPS and
leaves the default sinc5 filter.

Two data conversion modes are made available. When data is retrieved by
using the read_raw attribute, one shot single conversion mode is set.
The continuous conversion mode is enabled when the triggered buffer
mechanism is used. To assure correct data retrieval, the driver waits
for the interrupt triggered by the low to high transition of the DRDY
pin.

Datasheets:
Link: https://www.analog.com/media/en/technical-documentation/data-sheets/ad7768-1.pdfSigned-off-by: Stefan Popa <stefan.popa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -862,6 +862,13 @@ S:	Supported
 F:	drivers/iio/adc/ad7606.c
 F:	Documentation/devicetree/bindings/iio/adc/ad7606.txt
 
+ANALOG DEVICES INC AD7768-1 DRIVER
+M:	Stefan Popa <stefan.popa@analog.com>
+L:	linux-iio@vger.kernel.org
+W:	http://ez.analog.com/community/linux-device-drivers
+S:	Supported
+F:	drivers/iio/adc/ad7768-1.c
+
 ANALOG DEVICES INC AD9389B DRIVER
 M:	Hans Verkuil <hans.verkuil@cisco.com>
 L:	linux-media@vger.kernel.org

drivers/iio/adc/Kconfig

@@ -108,6 +108,19 @@ config AD7766
 	  To compile this driver as a module, choose M here: the module will be
 	  called ad7766.
 
+config AD7768_1
+	tristate "Analog Devices AD7768-1 ADC driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for Analog Devices AD7768-1 SPI
+	  simultaneously sampling sigma-delta analog to digital converter (ADC).
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad7768-1.
+
 config AD7791
 	tristate "Analog Devices AD7791 ADC driver"
 	depends on SPI

drivers/iio/adc/Makefile

@@ -15,6 +15,7 @@ obj-$(CONFIG_AD7606_IFACE_PARALLEL) += ad7606_par.o
 obj-$(CONFIG_AD7606_IFACE_SPI) += ad7606_spi.o
 obj-$(CONFIG_AD7606) += ad7606.o
 obj-$(CONFIG_AD7766) += ad7766.o
+obj-$(CONFIG_AD7768_1) += ad7768-1.o
 obj-$(CONFIG_AD7791) += ad7791.o
 obj-$(CONFIG_AD7793) += ad7793.o
 obj-$(CONFIG_AD7887) += ad7887.o