diff --git a/os/doc/init.txt b/os/doc/init.txt
index e8b3b8307..9c546810b 100644
--- a/os/doc/init.txt
+++ b/os/doc/init.txt
@@ -252,6 +252,34 @@ any sub configuration can be placed in a separate file specified via the
!
+Assigning subsystems to CPUs
+============================
+
+The assignment of subsystems to CPU nodes consists of two parts, the
+definition of the affinity space dimensions as used for the init process, and
+the association sub systems with affinity locations (relative to the affinity
+space). The affinity space is configured as a sub node of the config node. For
+example, the following declaration describes an affinity space of 4x2:
+
+!
+! ...
+!
+! ...
+!
+
+Subsystems can be constrained to parts of the affinity space using the
+'' sub node of a '' entry:
+
+!
+! ...
+!
+!
+! ...
+!
+! ...
+!
+
+
Priority support
================