How to set azure app gateway ingress in one namespace and target service istio-ingress is in another namespace in kubernetes?

Question

azure app gateway ingress in one namespace and target service istio-ingress is in another namespace, how to set that.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: server-ingress
  namespace: istio-ingress
  annotations:
    kubernetes.io/ingress.class: azure/application-gateway
    appgw.ingress.kubernetes.io/backend-protocol: "http"
    appgw.ingress.kubernetes.io/cookie-based-affinity: "true"
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  tls:
    - hosts:
        - dev1.myproduct.com
      secretName: product-cert-secret1
    - hosts:
        - dev2.myproduct.com
      secretName: product-cert-secret2
  rules:
    - host: dev1.myproduct.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: istio-ingress
                port:
                  number: 80
    - host: dev2.myproduct.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: istio-ingress
                port:
                  number: 80