How should I go about allowing specific miners to submit to the network?

[Bitcoin]

How should I go about allowing specific miners to submit to the network?

I have forked bitcoin, and I want to only allow mining submissions from specific public keys (I can verify the signature). Where would the best place to look in the bitcoin source? Would it be best to do it right at the rpc level, or somewhere else (i.e in a script, or in the consensus ~ validation.cpp)?

Alternativly, maybe I could check the coinbase tx and base validations on that?

Source: How should I go about allowing specific miners to submit to the network?