Creating a new port in C for use in guile

[Joshua Datko]

I want to make a new Port. I would like to write the port implementation
in C and use that port in scheme.

I'm a bit confused on how to proceed though. From reading the docs, it
seems I have to create a C function, in the form of an extension, that
calls scm_make_port_type.

However, the manual states [1] that the return value from
scm_make_port_type is a scm_ptob_descriptor. I'm confused on how I
instantiate this new port type to get a scm_port.

What am I missing?

Thanks,

Josh

[1] https://www.gnu.org/software/guile/manual/guile.html#Port-Implementation