The purpose of this pediatric study is to evaluate the drug levels, efficacy and safety of Deucravacitinib in children and adolescent participants aged 4 to \<18 years with moderate to severe plaque psoriasis. This study includes two cohorts; Cohort 1 (age 12 to \<18 years) and Cohort 2 (age 4 to \<12 years), with two parts; for each cohort. Part A will evaluate the drug levels of BMS-986165 to enable selection of 2 dose levels to be studied in Part B. Part B will assess the efficacy and safety of two dose levels in children and adolescent participants with moderate to severe plaque psoriasis. The 5-year long-term extension (LTE) period will observe the long-term safety and tolerability of deucravacitinib in children and adolescent participants with psoriasis who have completed Parts A or B of the study.