Rule #8.7 for "special function registers" and others?

[misra-c]

As Rule 8.7 deals with definitions, should the question be

Does this rule apply to objects which cannot be defined at block scope, like special function register variables?

There are a variety of methods by which special function registers might be defined, some (most or even all?) of which will involve language extensions in order to place the register at a particular location in the address space.

Could you please give an example of the kind of definition that you have in mind?