[PATCH v3 0/2] iio: adc: ad7944: new driver

[David Lechner <dlechner@baylibre.com>]

This is a new driver for the Analog Devices AD7944/AD7985/AD7986 family
of ADCs. These are fairly simple chips (e.g. no configuration registers).
The initial driver is only supporting the 'multi' (4-wire) SPI mode. We
plan to follow up with support for the 'single' (3-wire) SPI mode.

This work is done on behalf of Analog Devices, Inc., hence the
MAINTAINERS are @analog.com folks.

---
Changes in v3:
- Removed 'multi' value from adi,spi-mode property in DT bindings
- Modified driver for above change
- Fixed spelling of 'conventional'
- Added '#daisy-chained-devices' to DT bindings
- Added comments explaining that '3-wire' mode is not related to
  spi-3wire/SPI_3WIRE
- Replaced _sign with _diff in chip info struct to properly handle
  pseudo-differential vs. true differential chips
- Link to v2: https://lore.kernel.org/r/20240216-ad7944-mainline-v2-0-7eb69651e592@baylibre.com

Changes in v2:
- Added limit to spi-max-frequency for chain mode in DT bindings
- Added spi-cpol property to DT bindings
- Renamed '3-wire' mode to 'single' mode (to avoid confusion with spi-3wire)
- Renamed '4-wire' mode to 'multi' mode
- Dropped adi,reference property - now using only ref-supply and 
  refin-supply to determine the reference voltage source
- Fixed spelling of TURBO
- Renamed t_cnv to t_conv to match datasheet name and fixed comment
- Fixed wrong timestamp pushed to buffer
- Fixed scaling for chips with signed data
- Make use of sysfs_match_string() function
- Link to v1: https://lore.kernel.org/r/20240206-ad7944-mainline-v1-0-bf115fa9474f@baylibre.com

---
David Lechner (2):
      dt-bindings: iio: adc: add ad7944 ADCs
      iio: adc: ad7944: add driver for AD7944/AD7985/AD7986

 .../devicetree/bindings/iio/adc/adi,ad7944.yaml    | 213 +++++++++++
 MAINTAINERS                                        |   9 +
 drivers/iio/adc/Kconfig                            |  10 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ad7944.c                           | 413 +++++++++++++++++++++
 5 files changed, 646 insertions(+)
---
base-commit: 205bbf0d2dd2e0fcd6bf2a15b7df6fc570967e3b
change-id: 20240206-ad7944-mainline-17c968aa0967