The contents of these directories is sourced from Atmel's http://packs.download.atmel.com/ website.

* cmsis is "
CMSIS (Cortex Microcontroller Software Interface Standard)"
* samd21 is "Atmel SAMD21 Series Device Support"
* samd51 is " Atmel SAMD51 Series Device Support"

The atpack files have been unzipped into each respective directly and unmodified.