Collaboration with Riot

If a concept of something, champion, gameplay and basically any outside work that could be offered to Riot is done, what is a submission process? Just these boards? I would imagine this to get hard to navigate for a Rioter and a lot of stuff to "filter" through to put it politely.

If I had a rough draft of an Idea that might require some input from Riot to say "yay keep working or nay - nix the idea", how would that communique begin and continue to occur?