Re: [PATCH] docs: dt: writing-bindings: Extend compatible fallbacks guideline

[Rob Herring <robh@kernel.org>]

On Wed, Apr 15, 2026 at 03:46:41PM +0100, Conor Dooley wrote:
> On Wed, Apr 15, 2026 at 10:21:14AM +0200, Krzysztof Kozlowski wrote:
> > Extend the guidelines when to use fallback compatibles to cover to
> > common review responses.  Devices are most likely compatible and should
> > use fallbacks when having:
> > 
> > 1. Compatible programming interface, meaning one is a subset, and Linux
> >    device drivers can use the subset to correctly match/bind and still
> >    operate with the subset features.
> > 
> > 2. Device variant discovery through some means, like registers.
> > 
> > Devices are incompatible and fallback is not suitable when that
> > fallback cannot be used by the drivers to match/bind.
> > 
> > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
> > ---
> >  Documentation/devicetree/bindings/writing-bindings.rst | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/writing-bindings.rst b/Documentation/devicetree/bindings/writing-bindings.rst
> > index 667816dd7d50..03e29e2d50af 100644
> > --- a/Documentation/devicetree/bindings/writing-bindings.rst
> > +++ b/Documentation/devicetree/bindings/writing-bindings.rst
> > @@ -53,7 +53,12 @@ Properties
> >     - DON'T use wildcards or device-family names in compatible strings.
> >  
> >     - DO use fallback compatibles when devices are the same as or a superset of
> > -     prior implementations.
> > +     prior implementations.  Fallback compatibles are applicable especially
> > +     when sharing a programming interface or when able to discover the
> > +     variants.
> > +
> > +   - DON'T add fake fallback compatibles when software cannot use such to match
> > +     and bind to a device, and still operate correctly.
> >  
> >     - DO add new compatibles in case there are new features or bugs.
> 
> Acked-by: Conor Dooley <conor.dooley@microchip.com>
> 
>      - DO use the commit message explain why devices that may appear
>        compatible in a diff (e.g. no differences in property use) but
>        are not compatible, are not compatible.

Can you respin with Conor's addition.

Rob