Seems like someone that is progressing up the ranks. From defensive assistant in Miami to sharing secondary coaching duties in Atlanta, to now being the sole secondary coach in New York. All in a six year span. Bowles is very familiar with him.
http://www.nj.com/jets/index.ssf/2015/01/todd_bowles_jets_coaching_staff_beginning_to_take.html
Danna had been Atlanta's secondary coach since 2012. In Atlanta, Danna shared secondary coaching duties with Tim Lewis. Like Rodgers, Danna worked with Bowles in Miami. Danna was the assistant defensive backs coach there from 2010-11, so he basically worked alongside and under Bowles.
Danna was a defensive assistant with the Falcons from 2008-09. Before that, he coached defensive backs and wide receivers at the collegiate level. He played at Central Michigan from 1995-98.
http://www.nj.com/jets/index.ssf/2015/01/todd_bowles_jets_coaching_staff_beginning_to_take.html