The scarf hold has it's own set of strategies
Perhaps he is a grappler and has chosen the scarf hold, a lot of Judo players and wrestlers will opt for this
Perhaps it has followed a throw
Perhaps he is simply a strong person who has got you in a headlock and this has gone to the ground, or you have used the headlock defence takedown to make it a more even game for you, one of the tactics when you wish to go to the ground
You now need to work your headlock escape options, either the frappe escape that lets you take the mount, or the leg hook option that lets you take the back
With the frame escape option, take into consideration that he may keep the headlock on, so you will need to reflex drill the mount headlock escape options