Consider making a distinct, discoverable doc for IoT Hub Routing
Currently the routing docs are easily missed, mixed in with twin and job query docs. https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-query-language#device-to-cloud-message-routes-query-expressions
Explanations of IoTHub routing in general are insufficient. No effort is made to explain the background of why they are needed and what scenarios they should be used for.