On Tue, Jun 09, 2020 at 11:15:20AM -0600, Rob Herring wrote:

Find another driver doing this already and rename it 'simple-mfd' (no 
relation to the DT binding) and add your compatible string to it. 
'Generic' or 'simple' drivers don't require generic/simple DT bindings.

Or extend the existing syscon driver to look up the bus_type and create 
the regmap based on the bus type?

You'd need a particular bus driver to instantiate for a given bus (or
I'm misunderstanding your proposal) so it wouldn't even need a lookup,
just per-bus ID tables (and ideally also data tables with the regmap
and child descriptions).