Minimal example of peripheral SPI for Portenta H7

Hello,
I am trying to set up SPI communication between two Portenta H7's in order to facilitate _fast_ data transfer between them. The code for setting up the Portenta in controller ('master') mode is easy to follow and works fine (https://github.com/arduino/ArduinoCore-mbed/issues/131) - however, I have not been able to find any examples (minimal or otherwise) on how to setup the Portenta H7 as a _peripheral_ ('slave') SPI device. Does anyone know of such an example or resource?

Start with the Portenta H7 controller-mode setup referenced in issue #131 and inspect the ArduinoCore-mbed SPI examples or entry points. Done means providing a minimal, working peripheral-mode SPI example or clearly identifying an existing resource for communication between two Portenta H7 boards.

Written by the indexing model from the issue text.