What is the "software platform"?

I know that the “software model” was deprecated a long time ago. But today I was looking to learn how to write a plugin similar to the ANTLR plugin and ran across the term “Software Platform” while looking at Migrate antlr project to software platform · gradle/gradle@d91cc39 · GitHub .

What is the “Software Platform”?

I think that is just referring to how they restructured their source code layout.
Previously, it was in subprojects/antlr, now it is in platforms/software/antlr, the “software platform”.