<!-- Thanks for submitting this documentation request. Please fill the template below, otherwise we will not be able to process this request. --> #### Summary <!-- Summarize the request in a few sentences: --> Document upstream firmware upgrade procedure #### Why do we need this ? <!-- Please explain the motivation, for whom, etc. --> In order to have a clear documentation on how to upgrade upstream firmware present in this repository #### How do you propose to document this? <!-- Please think about how this could be fixed. --> `CONTRIBUTING.md`, containing a step-by-step guide #### Can you do this yourself and submit a Pull Request? <!-- You can also @mention experts if you need help with this. --> yes