Defining packages with a udev dependency

[Peter Polidoro <peter@polidoro.io>]

I would like to create a Guix package for PlatformIO so I can 
compile and upload firmware onto various embedded microprocessors.

The PlatformIO core is simply a pypi Python package, but it 
requires udev rules in order to communicate with the embedded 
devices.

I see that several Guix packages modify udev rules, for example 
libsigrok. Do these udev modifications work when using Guix on a 
foreign distro or do they only work when using Guix System?

Is simply installing the package enough to modify the udev rules 
or do they also need to be separately specified in the Guix System 
configuration?

When creating a new package that needs udev rules, is it better to 
create two packages, one for the rules and another for the package 
that require the rules, with one depending on the other? Or is it 
better to just create a single package with the udev modifications 
specified under arguments?

Thanks!