Route based on Classification here:
Admin -> Automation Rules -> [Initial Routing | Reclassification Routing] -> Add Rule
You would use something like:
Incident Classification -> Is Specific Classification -> [Root Classification[.Sub 1[.Sub 2[.Sub 3[.etc]]]]]
Then choose your action appropriately. You can choose to Continue which would allow running more rules on the same classification or Stop to terminate at this point. Just like firewall rules, order in these lists counts.