Reference for RPM spec macros (%setup, %buildroot, etc)
The Fedora Project hosts the best documentation on RPM out there in html format:
Prior to these resources, my go to guide was Maximum RPM (which you also found):
Some of them are documented in Maximum RPM, Taking the RPM Package Manager to the Limit by Edward C. Bailey.
Section Macros: Helpful Shorthand for Package Builders describes %setup and %patch macros.