My ds started with his early wakings at around the same age as well. He will go through spurts sometimes waking as early as 4:30am to start the day! They enter a really light stage of sleep at this time, and I always figured that for whatever reason he was just excited to start the day and no longer wanted to sleep. Some things that have helped us is putting him to bed earlier, even by 15 minutes or so, giving him a snack before bed so we know he is not hungry. The last time he did this I also made up my mind that enough was enough and that he was not leaving his room until 6am at the earliest. So when he cried out I would go to him and pick him up if need be offer him water and tell him it was still night time and time to go to sleep. He would cry and ask to go downstairs, ask for milk, ask for daddy, ask for the dog, etc., but i just kept telling him no, and giving him the message that his only option was to lie back down and cuddle with blankie. Once he was calm i would put him back down and leave, and sometimes he would fall asleep, and other times he would cry out again and I would repeat it all over again. This last episode was a few weeks ago and he has been sleeping until 6:30-7am since. I am sure he will have another episode again, but I will continue to keep doing this.
Hope this helps a bit!