I think it is essential to know about different clinical pictures in children struggling with mental health disorders. Some of these disorders have different phenotypical appearance. DSM gives you a guidelines. Whether we have a different DSM or not, clinical judment is very key to the dianostic process.
Yes, you can see the DC: 0-3R, a "developmentally based system for diagnosing mental health and developmental disorders in infants and toddlers" (https://www.zerotothree.org/resources/services/dc-0-3r). The updated manual, titled DC:0-5™, will be released in December 2016.