+# kernel_SUBDIRS .. subdirectories within which to propagate kernel targets
+# library_SUBDIRS .. list of subdirectories within which to propagate library targets
+# include_SUBDIRS .. list of subdirectories within which to propagate include pass (defaults to kernel_SUBDIRS + library_SUBDIRS)
+# binary_SUBDIRS .. list of subdirectories within which to propagate binary targets
+# docs_SUBDIRS .. list of subdirectories within which to propagate docs target
+# clean_SUBDIRS .. list of subdirectories within which to propagate clean targets