The overall design of the PEP-517 workflow needs to be documented. The specific classes (flit_core, setuptools_build_meta and pip_install_wheel) need to be documented. The variables defined in those classes need to be documented.
First pass: https://patchwork.yoctoproject.org/project/docs/patch/20220228035547.1134436-1-tim.orling@konsulko.com/
Changes were merged and later updated by Ross Burton.