What is the process of protocol change on Ethereum? How does the developers agree on some upgrade/update on the protocol?

I am interested to know about the process of changing any core protocol of Ethereum (e.g hard fork). Is it some kind of voting process? If yes, then who owns the voting rights? Can each ethereum node vote? Or can only those who mine transactions vote?
I was trying to think from institutional perspective. If any institution want to invest in the ethereum protocol, the first thing they would want to know is who controls/owns the protocol.