How would this be avoided? Or are you thinking of some kind of two-level
  component driver system:
  - the DSA switch is a component master, with components being its
    sub-devices such as internal PHYs etc
  - the DSA switch is also a component of the DSA switch tree

I think you might be missing a level. Think about the automotive
reference design system you posted the DT for a couple of days
ago. Don't you have cascaded switches, which are not members of the
same DSA tree. You might need a component for that whole group of
switches, above what you suggest here.

Can you nest components? How deep can you nest them?

    Andrew