In case the interrupt line is not available, polling can be used
to read out the state of the keys. Period of the polling needs to
be configured by the poll-interval DT property.
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>