Need help rewrite and redirect using ingress nginx

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1

Hi Forks,
I got a website running at example.com, currently i have a separated mobile path at example.com/mobile. I would like to bring it up at mobile.example.com (without subpath)
My ingress for mobile below

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/app-root: /mobile
    kubernetes.io/ingress.class: "nginx"
  name: mobile
  namespace: stage
spec:
  rules:
  - host: mobile.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: app
            port: 
              number: 80

Then it kept redirecting to mobile.example.com/mobile and made the url looks weird.
I also tried using ingress.kubernetes.io/rewrite-target: / but no luck.
Any suggestion would be highly appreciated. Thanks !