What's the difference between handleSubmit and onSubmit?

From what I can tell from every example I have seen, there is an unwritten – until now! – rule in the React community:

handleX is what you name the function that you pass to the onX prop.

render() {
  const handleClick = () => console.log('Clicked!');
  return <button onClick={handleClick}>Click me</button>;

Since the only way that redux-form can provide you with functionality is to pass it as a prop, it passes you a handleSubmit for you to pass to onSubmit.