Docs: Doxygen guidelines: Unclear API versioning for subgroups

Summary

The Doxygen guidelines for API versioning is unclear for subgroups: https://docs.zephyrproject.org/latest/contribute/style/doxygen.html#api-versioning

If there is an API group @defgroup Outer with @version 1.0.0, and there's a subgroup of that @defgroup Middle with @ingroup Outer, then does Middle need its own @since and @version, or is that optional?

If Middle is in the Outer group, can the Middle version be higher, e.g. Outer having @version 1.0.0 and Middle having @version 1.1.0?

What if there is a @defgroup Inner with @ingroup Middle and Middle does not have a @version; can Inner omit @version too, or will it inherent the version from Outer since Middle is in the Outer group?

Same questions above is unanswered for @since as well.

Describe the solution you'd like

Explicitly state in https://docs.zephyrproject.org/latest/contribute/style/doxygen.html#api-versioning how to work with multiple layers of groups, and whether @version is transient from e.g. Outer to Inner via Middle, or whether there's maximum number of levels of inheritance (or none)

Alternatives

No response

Additional Context

No response