Clean ran for a project will clean only the project files.
Clean-all ran for a project will clean also the library files on which the project depends.
The clean commands will only remove specific files and directories.
The top Makefile allows several options(per suggestion from jameyhicks):
make fmcomms1.zed will run "make all" in projects/fmcomms1/zed/
make clean will run "make clean" for all the projects
make clean-all will run "make clean" for all the projects and libraries
make lib will run "make all" for the library files
Adrian Costina