Travis Bickle. Jake LaMotta. Max Cady. De Niro has created so many indelible characters over the years, it would seem impossible for him to play an ordinary guy. But that’s just what he does, with stellar results, in “Silver Linings Playbook” as Pat Solitano Sr., father to Bradley Cooper’s recently released mental patient. Whether arguing with his Philadelphia neighbors over his beloved Eagles or trying to reason with Pat Jr. in a manic episode at 4 a.m., De Niro is completely believable as a regular Joe. Though he doesn’t always understand his son, the love he feels for him comes through.