Selling weapons and diplomatic support perhaps.
Direct intervention is unlikely, because Iran has always refused to enter any formal alliance with China or Russia. Iran is a very independent country, they don't want to join anyone's camp.
Perhaps they may change their mind about that in the coming months. If Iran wants a guarantee of direct intervention, or a nuclear umbrella, they will need to sign a mutual defense treaty.
But the best path of course, would be for Iran to develop their own nuclear weapons. The US Nuclear deal was just a stalling mechanism.