Its a penalty.
1. Ramires had the ball under 'control'. Reid never went for the ball.
2. Watch Reid RIGHT shoulder & elbow ACTIVE & swinging out towards Ramires to elbow him away from the ball. Ramires minimized the damage from elbowing nonetheless there was contact.
3. Professional Foul. Those who played football understand what Reid was trying to do. Watch Reid left shoulder dipped subtly for the 'elbowing'.
4. Ref Marriner was right there behind and saw Reid's shoulders & elbow ACTIONS.

Bottom line: Good Penalty Call for catching a professional foul.