docs(ROS 2): mention Zenoh middleware in main ROS 2 doc page

Signed-off-by: Beniamino Pozzan <beniamino.pozzan@gmail.com>

docs/en/middleware/uxrce_dds.md

@@ -31,6 +31,8 @@ The [eProsima micro XRCE-DDS _agent_](https://github.com/eProsima/Micro-XRCE-DDS
 The agent itself has no dependency on client-side code and can be built and/or installed independent of PX4 or ROS.
 
 Code that wants to subscribe/publish to PX4 does have a dependency on client-side code; it requires uORB message definitions that match those used to create the PX4 uXRCE-DDS client so that it can interpret the messages.
+An exception to the above rule is made by the _versioned_ PX4 msgs.
+Please refer to the [PX4 ROS 2 Message Transition Node](../ros2/px4_ros2_msg_translation_node.md) to know more about it.
 
 ## Code Generation
 
@@ -385,11 +387,14 @@ Therefore,
 - If you're using a main or release version of PX4 you can get the message definitions by cloning the interface package [PX4/px4_msgs](https://github.com/PX4/px4_msgs) into your workspace.
 - If you're creating or modifying uORB messages you must manually update the messages in your workspace from your PX4 source tree.
   Generally this means that you would update [dds_topics.yaml](https://github.com/PX4/PX4-Autopilot/blob/main/src/modules/uxrce_dds_client/dds_topics.yaml), clone the interface package, and then manually synchronize it by copying the new/modified message definitions from [PX4-Autopilot/msg](https://github.com/PX4/PX4-Autopilot/tree/main/msg) to its `msg` folders.
-  Assuming that PX4-Autopilot is in your home directory `~`, while `px4_msgs` is in `~/px4_ros_com/src/`, then the command might be:
+  Assuming that PX4-Autopilot is in your home directory `~`, while `px4_msgs` is in `~/ros2_px4_ws/src/`, then the command might be:
 
   ```sh
-  rm ~/px4_ros_com/src/px4_msgs/msg/*.msg
-  cp ~/PX4-Autopilot/msg/*.msg ~/px4_ros_com/src/px4_msgs/msg/
+  rm ~/ros2_px4_ws/src/px4_msgs/msg/*.msg
+  rm ~/ros2_px4_ws/src/px4_msgs/srv/*.srv
+  cp ~/PX4-Autopilot/msg/*.msg ~/ros2_px4_ws/src/px4_msgs/msg/
+  cp ~/PX4-Autopilot/msg/versioned/*.msg ~/ros2_px4_ws/src/px4_msgs/msg/
+  cp ~/PX4-Autopilot/srv/*.msg ~/ros2_px4_ws/src/px4_msgs/srv/
   ```
 
   ::: info

docs/en/ros2/index.md

@@ -15,17 +15,21 @@ It can be used, for example, for [computer vision](../computer_vision/index.md)
 ROS 2 enables a very deep integration with PX4, to the extent that you can create flight modes in ROS 2 that are indistinguisable from internal PX4 modes, and directly read from and write to internal uORB topics at high rate.
 It is recommended (in particular) for control and communication from a companion computer where low latency is important, when leveraging existing libraries from Linux, or when writing new high level flight modes.
 
-Communication between ROS 2 and PX4 uses middleware that implements the [XRCE-DDS protocol](../middleware/uxrce_dds.md).
-This middleware exposes PX4 [uORB messages](../msg_docs/index.md) as ROS 2 messages and types, effectively allowing direct access to PX4 from ROS 2 workflows and nodes.
-The middleware uses uORB message definitions to generate code to serialise and deserialise the messages heading in and out of PX4.
+Communication between ROS 2 and PX4 can leverage two independent middlewares:
+
+- [XRCE-DDS protocol](../middleware/uxrce_dds.md) - more tested and included by default in most PX4 builds.
+- [Zenoh protocol](../middleware/zenoh.md) - it needs to be manually enabled and added to PX4 builds.
+
+The middlewares expose PX4 [uORB messages](../msg_docs/index.md) as ROS 2 messages and types, effectively allowing direct access to PX4 from ROS 2 workflows and nodes.
+The middlewares use uORB message definitions to generate code to serialise and deserialise the messages heading in and out of PX4.
 These same message definitions are used in ROS 2 applications to allow the messages to be interpreted.
 
 ::: info
-ROS 2 can also connect with PX4 using [MAVROS](https://github.com/mavlink/mavros/tree/ros2/mavros) instead of XRCE-DDS.
+ROS 2 can also connect with PX4 using [MAVROS](https://github.com/mavlink/mavros/tree/ros2/mavros) instead of XRCE-DDS / Zenoh.
 This option is supported by the MAVROS project (it is not documented here).
 :::
 
-To use the [ROS 2](../ros2/user_guide.md) over XRCE-DDS effectively, you must (at time of writing) have a reasonable understanding of the PX4 internal architecture and conventions, which differ from those used by ROS.
+To use the [ROS 2](../ros2/user_guide.md) over XRCE-DDS / Zenoh effectively, you must (at time of writing) have a reasonable understanding of the PX4 internal architecture and conventions, which differ from those used by ROS.
 In the near term future we plan to provide ROS 2 APIs to abstract PX4 conventions, along with examples demonstrating their use.
 
 ## Topics
@@ -41,4 +45,5 @@ The main topics in this section are:
 
 ## Further Information
 
-- [XRCE-DDS (PX4-ROS 2/DDS Bridge)](../middleware/uxrce_dds.md): PX4 middleware for connecting to ROS 2.
+- [XRCE-DDS (PX4-ROS 2/DDS Bridge)](../middleware/uxrce_dds.md): PX4 middleware leveranging micro XRCE-DDS for connecting to ROS 2.
+- [Zenoh (PX4 ROS 2)](../middleware/zenoh.md): PX4 middleware leveraging Zenoh pico for connecting to ROS 2.