This change addresses API review feedback and improves documentation.
Specifically, it adds documentation for the newly added getMtu() and
getMacAddress() methods, describes under which conditions the MAC
address is null and adds a short blurb on how (or in what context) this
class is used.
Test: TH
Bug: 236187143
Change-Id: I349897fd55f3085ce88c8b94c84ec636bb5eb2a6
2af2ae8168