People view SRE in many difference ways. If you were to go through the Google SRE book, there's nothing explicit in there about building "platform" or doing any infrastructure engineering.

It's is a given that SRE build tooling, but most of the SRE-focused work, as described in that book is around improving the resilience of a given application or product. Addressing production readiness, defining SLOs, and handling incident response.

There are platform specific SRE teams at Google, but there's not much published about how they get about creating platform.

The book "Seeking SRE" makes it clear that in most places, the notion of "platform engineering" varies tremendously.

I don't know of any authors that have addressed this explicitly other than Susan Fowler in "Production Ready Microservices" who writes:

  Another important part of microservice adoption is the 
  creation of a microservice ecosystem. Typically (or, at 
  least, hopefully), a company running a large monolithic 
  application will have a dedicated infrastructure 
  organization that is responsible for designing, building, 
  and maintaining the infrastructure that the application runs 
  on. When a monolith is split into microservices, the 
  responsibilities of the infrastructure organization for 
  providing a stable platform for microservices to be 
  developed and run on grows drastically in importance. The 
  infrastructure teams must provide microservice teams with 
  stable infrastructure that abstracts away the majority of 
  the complexity of the interactions between microservices.