r(s) whose port(s) may be changed. When both Port
and SectionName are specified, the name and port of the selected listener
must match both specified values.

<gateway:experimental:description>
When the parent resource is a Service, this targets a specific port in the
Service spec. When both Port (experimental) and SectionName are specified,
the name and port of the selected port must match both specified values.
</gateway:experimental:description>

Implementations MAY choose to support other parent resources.
Implementations supporting other types of parent resources MUST clearly
document how/if Port is interpreted.

For the purpose of status, an attachment is considered successful as
long as the parent resource accepts it partially. For example, Gateway
listeners can restrict which Routes can attach to them by Route kind,
namespace, or hostname. If 1 of 2 Gateway listeners accept attachment
from the referencing Route, the Route MUST be considered successfully
attached. If no Gateway listeners accept attachment from this Route,
the Route MUST be considered detached from the Gateway.

Support: Extended9