Kubernetes - use secrets of other namespaces

Hi,

Can we use secret of other namespaces? Do we need to give Cluster level permissions to that namespace in which we want to use secret of other namespaces?

One of the ingress controller - ingress-nignx - can use a secret from other namespaces. It seems to use admission webhook or something.
https://github.com/kubernetes/ingress-nginx
https://kubernetes.github.io/ingress-nginx/user-guide/tls/#default-ssl-certificate