Gazebo standard ROS Rover Model and PX4 interfacing

Gazebo Rover Model

I have got a simple two wheeled differential drive model in Gazebo , I would like to control it with posix_sitl_default running a version of 50001_axial_racing_ax10 rover model that uses the simple controller defined in /example/rover_steering_control.

The rover model uses a differential drive plugin, called, a standard ROS plugin.

It expects cmd_vel topics, but PX4 STIL gazebo models seem to use /gazebo/command/motor_speed topics.

How could I map from one to the other? Ie how could I get the mavlink commands from PX4 SITL to the new gazebo model?

Or framing the question in more general terms: What are the steps to follow to add a new gazebo model to the PX4 gazebo infrastructure and be able to control it?