Handle categories and (nested) resources

I have an application, built with Rails 3.1.3, that has products and
categories. The categories are related to other categories, so a
category
can be a parent or a child category. The products are then related to a
child category.

Now, I’m thinking about how I should define the routes. Is it a good
idea
to somehow nest the categories and products resources? Ideally, I would
like URLs like this:

example.com/parent/child/product-1234

like this:
example.com/clothes/underwear/some-socks-1234

or maybe like this to keep it restful?
example.com/p/clothes/c/underwear/....

But maybe that’s a bit messy to achieve with the routes? I would have to
nest the category with itself I guess?

Any ideas on how to achieve something like this?

Do I create the category routes like this:

resources :categories, :as => "parent" do
    resources :categories, :as => "child"
end

or similar?
It’s not that important to have the product nested inside the
categories.
Maybe it will just make it hard to manage…

Maybe it is better to just create two models/controllers and nest them?
That way I get restful routes easily.