iio: addac: add AD74413R driver

The AD74412R and AD74413R are quad-channel software configurable input/output
solutions for building and process control applications. They contain
functionality for analog output, analog input, digital input, resistance
temperature detector, and thermocouple measurements integrated
into a single chip solution with an SPI interface.
The devices feature a 16-bit ADC and four configurable 13-bit DACs to provide
four configurable input/output channels and a suite of diagnostic functions.
The AD74413R differentiates itself from the AD74412R by being HART-compatible.

When configured with channel 0 as voltage output, channel 1 as current
output, channel 2 as voltage input and channel 3 as current input, the
following structure is created under the corresponding IIO device.

.
├── in_current0_offset
├── in_current0_raw
├── in_current0_sampling_frequency
├── in_current0_sampling_frequency_available
├── in_current0_scale
├── in_voltage1_offset
├── in_voltage1_raw
├── in_voltage1_sampling_frequency
├── in_voltage1_sampling_frequency_available
├── in_voltage1_scale
├── in_voltage2_offset
├── in_voltage2_raw
├── in_voltage2_sampling_frequency
├── in_voltage2_sampling_frequency_available
├── in_voltage2_scale
├── in_current3_offset
├── in_current3_raw
├── in_current3_sampling_frequency
├── in_current3_sampling_frequency_available
├── in_current3_scale
├── out_voltage0_raw
├── out_voltage0_scale
├── out_current1_raw
├── out_current1_scale
├── name
├── buffer
│   ├── data_available
│   ├── enable
│   ├── length
│   └── watermark
└── scan_elements
    ├── in_current0_en
    ├── in_current0_index
    ├── in_current0_type
    ├── in_voltage1_en
    ├── in_voltage1_index
    ├── in_voltage1_type
    ├── in_voltage2_en
    ├── in_voltage2_index
    ├── in_voltage2_type
    ├── in_current3_en
    ├── in_current3_index
    └── in_current3_type

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>

MAINTAINERS

@@ -1069,6 +1069,15 @@ W:	http://ez.analog.com/community/linux-device-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad7780.yaml
 F:	drivers/iio/adc/ad7780.c
 
+ANALOG DEVICES INC AD74413R DRIVER
+M:	Cosmin Tanislav <cosmin.tanislav@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	http://ez.analog.com/community/linux-device-drivers
+F:	Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml
+F:	drivers/iio/addac/ad74413r.c
+F:	include/dt-bindings/iio/addac/adi,ad74413r.h
+
 ANALOG DEVICES INC AD9389B DRIVER
 M:	Hans Verkuil <hverkuil-cisco@xs4all.nl>
 L:	linux-media@vger.kernel.org

drivers/iio/addac/Kconfig

@@ -5,4 +5,16 @@
 
 menu "Analog to digital and digital to analog converters"
 
+config AD74413R
+	tristate "Analog Devices AD74412R/AD74413R driver"
+	depends on GPIOLIB && SPI
+	select REGMAP_SPI
+	select CRC8
+	help
+	  Say yes here to build support for Analog Devices AD74412R/AD74413R
+	  quad-channel software configurable input/output solution.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad74413r.
+
 endmenu

drivers/iio/addac/Makefile

@@ -4,3 +4,4 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AD74413R) += ad74413r.o