Why are generic arguments used instead of direct interface/abstract classes names?

Question

Let's say you've got a method which takes a class which is an instance of the interface Parent as the first and only parameter, just like this one:

public void doSomething(Parent parent) {}

Let's also say we've got a class Child which implements the interface Parent.

Why are many people using this method head:

public <T extends Parent> doSomething(T parent) {}

instead of this one:

public void doSomething(Parent parent) {}

Are there any advantages? Thanks for your help!