Portsmouth were relegated from the Premiership last season and are in administration due to their horrendous financial situation. They are only allowed to sign free agents, so Dorman fits the bill perfectly.
There are suggestions the Welsh international would earn five times more than he was on at Saints, but this in turn is probably very little compared to what Pompey were paying their players last season.
The move would probably be good for both parties, but it would be a surprise if more Championship clubs don't go chasing the 28-eight-year old in the near future.
In other former Saints news, it would seem ex-manager Gus MacPherson is now one of the favourites for the vacant manager's job at Kilmarnock.