Add MAX22530-MAX22532 ADC Support

Hello iio/maintainers,

This patch series adds initial support for the Analog Devices Maxim family of MAX22530-MAX22532 ADCs. These are galvanically isolated, 4-channel, multiplexed, 12-bit, analog-to-digital converters (ADC) in the MAXSafe™ family product line. An integrated, isolated, DC-DC converter powers all fieldside circuitry, and this allows field-side diagnostics even when no input signal is present.

The first patch adds the device tree documentation for the ADC. The DT binding has been verified with DT_BINDING_CHECK. The second patch adds the read functionality for raw and average ADC values from registers.

The code was tested with Raspberry Pi5 and MAX22531_EVKIT_A. With the current driver version, it is possible to do single-shot read of ADC sample data. On a preliminary version of the max22531 driver with debugfs_reg_access callbacks, it was also possible to read/write from/to different device registers and obtain the expected results.

Details of the test setup can be found at
https://wiki.analog.com/resources/tools-software/linux-drivers/iio-adc/max22531

This code was developed as part of the GSoC project for Linux Foundation. Many thanks to my mentors Marcelo Schmitt, Ceclan Dumitru, Jonathan Santos & Dragos Bogdan for their guidance and reviews throughout the course of this programme.

Abhinav Jain (2):
dt-bindings: iio: adc: Add device tree binding for MAX22531 ADC
iio: adc: Add initial support for MAX22531 ADC

 .../bindings/iio/adc/adi,max22531.yaml        |  75 +++++++
 MAINTAINERS                                   |   8 +
 drivers/iio/adc/Kconfig                       |  10 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max22531.c                    | 191 ++++++++++++++++++
 5 files changed, 285 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
 create mode 100644 drivers/iio/adc/max22531.c

base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494

2.34.1