The <switchPort> element defines a mapping to a subset of the
<switch> element's components. All references to an internal switch
component must be made through a <switchPort> element or, by default,
to the <switch> element without specifying any <switchPort>. In
this last case, it is considered as if the reference is made to a default
<switchPort> that contains mapping elements to each child object of the
switch and referring to their whole content anchors.