The former Burnley midfielder has joined Newcastle in a Bosman deal.
Martin told theEvening Chronicle: "I've seen him play many times going back to my involvement with the Ireland FA.
"I monitored players for the Ireland national side so I have met him a few times at the squad hotel in Dublin. I know he's a North Sider from Dublin like me.
"I'd like to welcome him to the area and the club. I've watched him from an early age and I've always liked what I seen."
Martin added: "The thing about him is he always gets through his work.
"He is capable of getting you four or five goals a season from the middle of the park which is a huge plus.
"He has the grittiness for midfield in his locker if he needs to use it. But he's more the type of guy you want to see get on the ball.
"You'd rather see him push forward and I'd like to see him partnered with Jonjo Shelvey because he makes the runs forward.
"I wouldn't classify him as a physical player, but he can handle that part of the game.
"His assets are to link up with the strikers, make runs and create chances to score goals."