I've splitted it to7 patches. each patch split one <sect1> into separate new files.
Seems like a good start. Looking at the diffs of these, I wonder if we would be better off with a func/ directory, each function gets its own file in that dir, and either these files above include the individual files, or the original func.sgml just becomes the organizer of all the functions. That would allow us to do future reorganizations with minimal churn, make validation of this patch a bit more straightforward, and make it easier for future editors to find the function they need to edit.