Add release notes

Author: saikishor

doc/release_notes.rst

@@ -21,7 +21,20 @@ For details see the controller_manager section.
 * Pass controller manager update rate on the init of the controller interface  (`#1141 <https://github.com/ros-controls/ros2_control/pull/1141>`_)
 * 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.
+* 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.
 * The controllers will now set ``use_global_arguments`` from `NodeOptions <https://docs.ros.org/en/rolling/p/rclcpp/generated/classrclcpp_1_1NodeOptions.html#_CPPv4N6rclcpp11NodeOptions20use_global_argumentsEb>`__ to false, to avoid getting influenced by global arguments (Issue : `#1684 <https://github.com/ros-controls/ros2_control/issues/1684>`_) (`#1694 <https://github.com/ros-controls/ros2_control/pull/1694>`_). From now on, in order to set the parameters to the controller, the ``--param-file`` option from spawner should be used.
 * With (`#1683 <https://github.com/ros-controls/ros2_control/pull/1683>`_) the ``rclcpp_lifecycle::State & get_state()`` and ``void set_state(const rclcpp_lifecycle::State & new_state)`` are replaced by ``rclcpp_lifecycle::State & get_lifecycle_state()`` and ``void set_lifecycle_state(const rclcpp_lifecycle::State & new_state)``. This change affects controllers and hardware. This is related to (`#1240 <https://github.com/ros-controls/ros2_control/pull/1240>`_) as variant support introduces ``get_state`` and ``set_state`` methods for setting/getting state of handles.
 * The ``assign_interfaces`` and ``release_interfaces`` methods are now virtual, so that the user can override them to store the interfaces into custom variable types, so that the user can have the flexibility to take the ownership of the loaned interfaces to the controller (`#1743 <https://github.com/ros-controls/ros2_control/pull/1743>`_)