Elegran
I would treat it as a training exercise, rather than a regular responsibility that you are taking on for ever. Agree a reasonable time for him to be up an about, and at that time, stick your head round the bedroom door and say loudly "I am putting on your porridge NOW" He sounds quite happy for you to wake him, so he shouldn't (?) be grumpy when you do, but if he hasn't appeared by the time the porridge (or whatever his choice is) is out on the plate, go back and tell him it is ready. If he still doesn't appear in a few minutes, return to say that it is uneatable and you have thrown it out.
After a week or two of this, his stomach should be reminding him that this is time to eat. It may be sooner, it may take longer.
I’d let him get his own porridge! Or whatever he has for breakfast.
My dh gets his own breakfast and lunch - we are often up at different times and I never want anything to eat first thing.
The only meal we eat together is dinner, which I do cook.
