We need to add a section in https://docs.openshift.com/serverless/1.34/knative-serving/external-ingress-routing/configuring-service-routes.html::

 `haproxy.router.openshift.io/timeout` for auto-generated routes can now be configured through Operator Subscription for OpenShift Serverless:

apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
...
spec:
  channel: stable
  config:
    env:
      - name: ROUTE_HAPROXY_TIMEOUT
        value: '900'

Alternatively, you can disable the route generation for the specific service and manually create the route along with the corresponding timeout.