What does a pediatric psychiatrist take care of? What kinds of disorders?

Child psychiatrists. Child ("pediatric") psychiatrists specialize in the diagnosis and the treatment of disorders of thinking, feeling and/or behavior affecting children, adolescents, and their families. They provide comprehensive care for these patients & their families, from the perspective of their medical education and training. http://www.aacap.org/cs/root/facts_for_families/the_child_and_adolescent_psychiatrist.
Pediatric. Child psychiatrist cares for all developmental disorders, disorders of early years such ad pervasive developmental disorders or reactive attachment disorders or separation anxiety disorders, as well as other disorders seen in children/adolescents such as substance abuse, psychoses or mood disorders.
Psychiatrist. Any mental health concerns where an evaluation is needed and/or medications in children falls under the purview of a pediatric psychiatrist.