Group Policy Inheritance in Child Domain

Is a child domain within ADS a child object of the root domain?

I want to apply a root domain group policy to all child domains (i.e. apply test.local policy to child1.test.local & child2.test.local).

Now the only way I have managed this is tolink the root domain policy to the child domains. If the child domains are considered to be child objects of the root domain, should the root domain GPO be applied to them, in Microsoft?s terms, ?by design??

Regards,
Tictag.