docs(joint_state_broadcaster): clarify /dynamic_joint_states contents (backport #1865) (#1870)

Author: mergify[bot]

joint_state_broadcaster/doc/userdoc.rst

@@ -20,6 +20,42 @@ In the latter case, resulting interfaces is defined by a "matrix" of interfaces
 If some requested interfaces are missing, the controller will print a warning about that, but work for other interfaces.
 If none of the requested interface are not defined, the controller returns error on activation.
 
+Published topics
+----------------
+
+* ``/joint_states`` (``sensor_msgs/msg/JointState``):
+
+  Publishes *movement-related* interfaces only — ``position``, ``velocity``,
+  and ``effort`` — for joints that provide them. If a joint does not expose a given
+  movement interface, that field is omitted/left empty for that joint in the message.
+
+* ``/dynamic_joint_states`` (``control_msgs/msg/DynamicJointState``):
+
+  Publishes **all available state interfaces** for each joint. This includes the
+  movement interfaces (position/velocity/effort) *and* any additional or custom
+  interfaces provided by the hardware (e.g., temperature, voltage, torque sensor
+  readings, calibration flags).
+
+  The message maps ``joint_names`` to per-joint interface name lists and values.
+  Example payload::
+
+    joint_names: [joint1, joint2]
+    interface_values:
+      - interface_names: [position, velocity, effort]
+        values: [1.5708, 0.0, 0.20]
+      - interface_names: [position, temperature]
+        values: [0.7854, 42.1]
+
+  Use this topic if you need *every* reported interface, not just movement.
+
+.. note::
+
+   If ``use_local_topics`` is set to ``true``, both topics are published in the
+   controller’s namespace (e.g., ``/my_state_broadcaster/joint_states`` and
+   ``/my_state_broadcaster/dynamic_joint_states``). If ``false`` (default),
+   they are published at the root (e.g., ``/joint_states``).
+
+
 Parameters
 ----------
 This controller uses the `generate_parameter_library <https://github.com/PickNikRobotics/generate_parameter_library>`_ to handle its parameters. The parameter `definition file located in the src folder <https://github.com/ros-controls/ros2_controllers/blob/{REPOS_FILE_BRANCH}/joint_state_broadcaster/src/joint_state_broadcaster_parameters.yaml>`_ contains descriptions for all the parameters used by the controller.