Feature, classes, use relative reference

Change-Id: I1942580e78d3c9e83fdad4927532186441fe3298
diff --git a/README-extentions.rst b/README-extentions.rst
index 2bc4816..6693256 100644
--- a/README-extentions.rst
+++ b/README-extentions.rst
@@ -336,6 +336,37 @@
     ...
 
 
+Load classes with relative names
+--------------------------------
+
+Load referenced class from a relative location to the current class.
+To load class from relative location start the class uri with "." char.
+The only supported reference is to nested tree structure below the current class.
+
+You are allowed to use syntax for relative uri to required class on any place on your model (first class loaded, init.yml, regular class .yml).
+
+The feature is expected to improve flexibility while sharing classes between your models.
+
+It's a new feature use it with care and mind that using "relative syntax" lower traceability of
+your pillar composition.
+
+Example usage of relative class name:
+
+.. code-block:: yaml
+
+  #/etc/reclass/classes/component/defaults.yml
+  classes:
+    component:
+      config:
+        a: b
+
+.. code-block:: yaml
+
+  #/etc/reclass/classes/component/init.yml
+  classes:
+    - .defaults
+
+
 Inventory Queries
 -----------------