input: Adding definitions for recovery and maskrom button?

[Sebastian Kropatsch <seb-dev@mail.de>]

Hello!

Many Single Board Computers (SBCs), especially those based on Rockchip
SoCs, come with on-board buttons labeled "Recovery" (for entering some
recovery mode) and "MaskROM" (for entering MaskROM mode for software
flashing). These are usually GPIO-based keys or ADC attached resistor
ladder buttons.

When defining devicetrees for these boards, the current approaches
include e.g. using "linux,code = <KEY_VENDOR>;", <KEY_SETUP>,
<KEY_PROG2> or <BTN_1> if these butons are even defined in the
devicetree source. So basically, there is no common approach
currently, since a clearly defined key label is missing.

The "linux,code" symbols used in the .dts files come from
"include/uapi/linux/input-event-codes.h" which is included by
"#include <dt-bindings/input/input.h>".

Would it be a sensible approach to add two defines to input-event-codes.h
e.g. KEY_RECOVERY and KEY_MASKROM (or a more generalized name)? Or is
this out-of-scope for input-event-codes.h?

Please let me know. Thanks! I can send a patch if I get green light :)

In case you'd like to see examples of these buttons, you may have
a look at devices like FriendlyElec NanoPC T6 [1] or Orange Pi 5 Plus [2].


Cheers,
Sebastian

[1] https://wiki.friendlyelec.com/wiki/index.php/NanoPC-T6
[2] http://www.orangepi.org/orangepiwiki/index.php/Orange_Pi_5_Plus