Have things alphabetically, not subject oriented. AR for business reasons. PJ this is not true. No, this is not needed. But not really - subject oriented Shell.
Some overriding things can go into a chapter heading if chapter oriented.
JZ ISO and IEEE want to make money by selling paper. The final version must be one source, of something that will be rendered on paper. There may be other electronic guides to this material. Each section could be logically tagged to help in presenting it in alternative formats. Overarching requirements, covering several functions, go into common header file descriptions.