examples-3.x-dev/modules/field_permission_example/field_permission_example.routing.yml

field_permission_example.description:
  path: '/examples/field-permission-example'
  defaults:
    _title: 'Field Permission Example'
    _controller: '\Drupal\field_permission_example\Controller\FieldPermissionExampleController::description'
  requirements:
    _permission: 'access content'