--- a/doc/makefile-variables.txt	Wed Jan 28 15:28:28 2015 -0800
+++ b/doc/makefile-variables.txt	Thu Jan 29 08:52:10 2015 -0800
@@ -92,6 +92,11 @@
 but your component Makefile might have to += some more for specific transforms
 that need to be applied to the test output for just this component.
 
+* SKIP_TEST_AT_TOP_LEVEL inclusion of this variable in a component Makefile
+  will cause that component's tests to be skipped when running "gmake test"
+  at the top level.  It's often used for excluding long-running tests 
+  that may slow down comprehensive component testing.  
+
 * COMPONENT_POST_UNPACK_ACTION is for making minor alterations to the unpacked
   source directory before any patching has taken place.  It should almost never
   be used.