How do I get the key type hints for deep object?

Question

let Bob = {
    age: 24,
    name: 'bob',
    son: {
        foo: {
            age: 2,
        },
    },
}
const doSomething = (deepKey: any) => {
    // doSomething
}
// I want to have a type hint
doSomething('son.foo.age')

I want to have a literal type hint, What do I do with deepKey to get a literal type hint ?