sched: better rt-group documentation

Viktor was nice enough to enhance the document based on my replies to
his questions on the subject.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

init/Kconfig

diff --git a/init/Kconfig b/init/Kconfig
index 7fccf09..ba3a389 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -328,6 +328,13 @@
 	depends on EXPERIMENTAL
 	depends on GROUP_SCHED
 	default n
+	help
+	  This feature lets you explicitly allocate real CPU bandwidth
+	  to users or control groups (depending on the "Basis for grouping tasks"
+	  setting below. If enabled, it will also make it impossible to
+	  schedule realtime tasks for non-root users until you allocate
+	  realtime bandwidth for them.
+	  See Documentation/sched-rt-group.txt for more information.
 
 choice
 	depends on GROUP_SCHED