Smith served as Penn State's offensive analyst and analytics coordinator for the last two seasons.
Mills will attend his third school after attending Lackawanna Community College before Penn State.
Barkley, along with three other Penn Staters are set to represent the Nittany Lions in this year's Super Bowl.
According to FootballScoop, Penn State offered Knowles $3.2 million a year.
Saquon Barkley, Saquon Barkley, and Saquon Barkley.
Knowles comes to Happy Valley with 36 years of coaching experience.