For e.g. doing an arm build you need ports add-on. So the instructions
does not specify anything about ports directory where to put it
etc. for ppc ports is not needed so even if ports in not there is will
work.
but may be we could add some words on how to configure ports along
with libc. I saw that the configure already has --enable-add-ons so
creating a symlink inside libc directory to ports would be sufficient
If you're using a target that depends on ports, the ports/README file
already explains how to use it, mentioning the copy-into and
--enable-add-ons approaches. I'd have to say I think that's probably
the best place for those instructions.