[TOPIC: DTS] dts: bindings: Have 'required: true/false' instead of 'category: ...' (take two, edtlib version)

[ulfalizer]

The 'category: required/optional' setting for properties is just a
yes/no thing. Using a boolean makes it clearer, so have
'required: true/false' instead.

Print a clear error when 'category:' is used:

edtlib.EDTError: please put 'required: true' instead of 'category:
required' in 'properties: foo: ...' in
test-bindings/sub-node-parent.yaml - 'category' has been removed

The old scripts in scripts/dts/ ignore this setting, and only print a
warning if 'category: required' in an inherited binding is changed to
'category: optional'. Remove that code, since the new scripts already
have the same check.

The replacement was done with

git ls-files 'dts/bindings/*.yaml' | xargs sed -i \
    -e 's/category:\s*required/required: true/' \
    -e 's/category:\s*optional/required: false/'

dts/binding-template.yaml is updated as well.

[ulfalizer]

Another thing I've been thinking about:

required: true would probably be a better default than required: false, since there are a lot more required properties than optional ones. It would completely get rid of required: from many bindings.

The default when required: is missing doesn't seem to be documented now either, so there might be properties that ought to be required that aren't.

Any thoughts?

I also considered the json-schema version, where you list all the required properties separately at the top level:

required:
    - foo
    - bar
    - baz

I couldn't think of any technical advantages compared to what we have though, and there are a few disadvantages:

• It's inconsistent with how other property settings are specified, and moves information away from the property specification

• It makes it impossible to default to required, unless we have optional: or something instead.

  (This seems to be a pretty common complaint re. json-schema. See e.g. Require all described properties. json-schema-org/json-schema-spec#562 and https://stackoverflow.com/questions/30868023/json-schema-require-all-properties.)

• It makes it impossible to change a property from an inherited binding from required to optional. Maybe that'd be nice in some cases (or an anti-feature, not sure).

[galak]

Another thing I've been thinking about:

required: true would probably be a better default than required: false, since there are a lot more required properties than optional ones. It would completely get rid of
required: from many bindings.

The default when required: is missing doesn't seem to be documented now either, so there might be properties that ought to be required that aren't.

Did we require category to be set before? Hmm, wonder if its better to keep it explicit and enforce that 'required' be provided.

Any thoughts?

Kinda related, we need to clean up the overriding of required. I think there's a binding that fails today, but it isn't used in any default code so we don't see the issue.