iio: addac: add AD74115 driver

The AD74115H is a single-channel, software-configurable, input and
output device for industrial control applications. The AD74115H
provides a wide range of use cases, integrated on a single chip.

These use cases include analog output, analog input, digital output,
digital input, resistance temperature detector (RTD), and thermocouple
measurement capability. The AD74115H also has an integrated HART modem.

A serial peripheral interface (SPI) is used to handle all communications
to the device, including communications with the HART modem. The digital
input and digital outputs can be accessed via the SPI or the
general-purpose input and output (GPIO) pins to support higher
speed data rates.

The device features a 16-bit, sigma-delta analog-to-digital converter
(ADC) and a 14-bit digital-to-analog converter (DAC).
The AD74115H contains a high accuracy 2.5 V on-chip reference that can
be used as the DAC and ADC reference.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20221117080916.411766-3-cosmin.tanislav@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -1181,6 +1181,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	http://ez.analog.com/community/linux-device-drivers
 F:	Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml
+F:	drivers/iio/addac/ad74115.c
 
 ANALOG DEVICES INC AD74413R DRIVER
 M:	Cosmin Tanislav <cosmin.tanislav@analog.com>

drivers/iio/addac/Kconfig

@@ -5,6 +5,20 @@
 
 menu "Analog to digital and digital to analog converters"
 
+config AD74115
+	tristate "Analog Devices AD74115H driver"
+	depends on GPIOLIB && SPI
+	select CRC8
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select REGMAP_SPI
+	help
+	  Say yes here to build support for Analog Devices AD74115H
+	  single-channel software configurable input/output solution.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad74115.
+
 config AD74413R
 	tristate "Analog Devices AD74412R/AD74413R driver"
 	depends on GPIOLIB && SPI

drivers/iio/addac/Makefile

@@ -4,5 +4,6 @@
 #
 
 # When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AD74115) += ad74115.o
 obj-$(CONFIG_AD74413R) += ad74413r.o
 obj-$(CONFIG_STX104) += stx104.o