godot/misc/dist/linux/org.godotengine.Godot.xml

<?xml version="1.0"?>
 <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
   <mime-type type="application/x-godot-project">
   <comment>Godot Engine project</comment>
   <icon name="godot" />
   <glob pattern="*.godot" weight="100" />
  </mime-type>
</mime-info>