siox: Provide a devm variant of siox_master_register()

This allows to simplify siox master drivers in the next step.

Acked-by: Thorsten Scherer <t.scherer@eckelmann.de>
Link: https://lore.kernel.org/r/e961dfb3e94f106b16f5eacff2110fc7fa0cab13.1708328466.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

siox: Provide a devm variant of siox_master_alloc()

This allows to simplify siox master drivers in the next step.

Acked-by: Thorsten Scherer <t.scherer@eckelmann.de>
Link: https://lore.kernel.org/r/ad141dd22c7d95ad0bd347f257ce586e1afb22a4.1708328466.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

siox: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header file related to Eckelmann SIOX driver.
For C header files Documentation/process/license-rules.rst
mandates C-like comments (opposed to C source files where
C++ style should be used).

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.

Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Thorsten Scherer <thorsten.scherer@eckelmann.de>
Link: https://lore.kernel.org/r/20200101131418.GA3110@nishad
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

siox: new driver framework for eckelmann SIOX

SIOX is a bus system invented at Eckelmann AG to control their building
management and refrigeration systems. Traditionally the bus was
implemented on custom microcontrollers, today Linux based machines are
in use, too.

The topology on a SIOX bus looks as follows:

,------->--DCLK-->---------------+----------------------.
^ v v
,--------. ,----------------------. ,------
| | | ,--------------. | |
| |--->--DOUT-->---|->-|shift register|->-|--->---|
| | | `--------------' | |
| master | | device | | device
| | | ,--------------. | |
| |---<--DIN---<---|-<-|shift register|-<-|---<---|
| | | `--------------' | |
`--------' `----------------------' `------
v ^ ^
`----------DLD-------------------+----------------------'

There are two control lines (DCLK and DLD) driven from the bus master to
all devices in parallel and two daisy chained data lines, one for input
and one for output. DCLK is the clock to shift both chains by a single
bit. On an edge of DLD the devices latch both their input and output
shift registers.

This patch adds a framework for this bus type.

Acked-by: Gavin Schenk <g.schenk@eckelmann.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>