There are a few different ways to do this, depending on your needs, and more knowledgeable people will help with that.
Your diagram isn't complete, obviously, but what it seems to me to be missing is that the solar
charges the battery
. None of your appliances run off the solar panel
. Everything runs off the battery
So in it's most simple form, you just wire the solar
right to the battery and skip all the other camper electronics. What I just did recently is put a panel on my roof, run the wires into the camper, to the charge controller which I mounted as close to the battery as possible, up near the front interior close to the tongue. The panel runs to the controller, the controller runs to the battery. I have a fuse between the controller and battery. Other than charging the battery, the solar is completely isolated from the trailer wiring.