How to propose / upload GPIO improvements to the source tree?

[ogroot]

I updated Gpio.cpp in order to be able to use the extra 9 GPIO ports of the Pi2.
The current version of Gpio.cpp was limited to the old number of GPIO ports of the Pi A/B.

I compiled, tested and used the new build. But I can imagine that other people also want to use this.

How can I upload my "improved Gpio.cpp" to the source tree ??
Is there a quide / instruction somewhere?