iio: chemical: sgpxx: Support SGP30 / SGPC3 Gas Sensors

This patch series adds support for Sensirion SGP30 and SGPC3 I2C gas sensors.

Patch 1/2 adds full driver support and sensor documentation Patch 2/2 adds triggered buffer support

Note that the current version of libiio (0.11) has some parsing issues with the use of struct iio_chan_spec's extend_name. Patches will be issued separately, but reviewers are kindly asked to ensure that this patch follows best IIO attribute naming practises.

Further product specs available from:
https://www.sensirion.com/en/environmental-sensors/gas-sensors/multi-pixel-gas-sensors/

Andreas Brauchli (2):
iio: chemical: sgpxx: Support Sensirion SGPxx sensors
iio: chemical: sgpxx: triggered buffer support

 Documentation/iio/chemical/sgpxx.txt | 112 +++++
 drivers/iio/chemical/Kconfig         |  16 +
 drivers/iio/chemical/Makefile        |   1 +
 drivers/iio/chemical/sgpxx.c         | 932 +++++++++++++++++++++++++++++++++++
 4 files changed, 1061 insertions(+)
 create mode 100644 Documentation/iio/chemical/sgpxx.txt
 create mode 100644 drivers/iio/chemical/sgpxx.c

2.14.1