Does any one treat discoid lupus?

Yes: Any dermatologist can manage, but not cure, common discoid lupus. You already know to avoid sunlight. Topical or intralesional glucocorticoids have been standard for decades. Systemic Chloroquine or a similar drug are often helpful as well. Topical calcineurin inhibitors are a relatively new addition, and there are reports of success with topical retinoic acid derivatives.