Add release notes

Author: saikishor

doc/release_notes.rst

@@ -22,6 +22,20 @@ For details see the controller_manager section.
 * A method to get node options to setup the controller node #api-breaking (`#1169 <https://github.com/ros-controls/ros2_control/pull/1169>`_)
 * Export state interfaces from the chainable controller #api-breaking (`#1021 <https://github.com/ros-controls/ros2_control/pull/1021>`_)
 * All chainable controllers must implement the method ``export_state_interfaces`` to export the state interfaces, similar to ``export_reference_interfaces`` method that is exporting the reference interfaces.
+* Controllers can now be able to remap the interfaces they are going to claim from the controller_manager. For instance, this can be used when a controller is going to claim the ``effort`` interface but the hardware exposes a different interface such as ``torque`` or ``force`` or ``current`` etc. This can be easily defined in the controller configuration file as shown below (`#1667 <https:://github.com/ros-controls/ros2_control/pull/1667>`_)
+
+  .. code-block:: yaml
+
+    <controller_name>:
+      ros__parameters:
+        type: <controller_type>
+        remap:
+          state_interfaces:
+            "<joint>/effort": "<joint>/torque"
+          command_interfaces:
+            "<joint>/effort": "<joint>/torque"
+
+  In the above example, the controller is going to claim the ``effort`` interface but the hardware exposes the ``torque`` interface. By defining the above remapping definition, The controller will claim the ``torque`` interface instead of the ``effort`` interface.
 
 controller_manager
 ******************