We have method passthru that is accepting parameter async,
but since python 3.7 use async as reserved word,
the async parameter is deprecated,
async_call should be used instead.
async parameter will be removed in the next cycle.
Change-Id: I6299aafd30faae9a93df2cb901c1505df47e6b45
Task: 9289
Story: 1751306
Also write a bit more meaningful documentation on writing drivers with
helpful links to move forward.
Change-Id: Id76705efabaf93a76a1370bc2e1d998622e82ac9
Partial-Bug: #1690185