The binding table provides four different lookup functions, which
purpose is not obvious neither by their names nor by the (lack of)
descriptions.

We now give these functions names that better match their purposes,
and improve the comments that describe what they are doing.
Signed-off-by: NJon Maloy <jmaloy@redhat.com>
Acked-by: NYing Xue <ying.xue@windriver.com>
Acked-by: NHoang Le <hoang.h.le@dektech.com.au>
Acked-by: NTung Nguyen <tung.q.nguyen@dektech.com.au>
Acked-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>