Add regulated 5v input pin to homemade arduino uno

Recently i've made my own Arduino Uno (atmega328p-pu). I've followed the tutorial on the arduino playground, but the problem is that i can only power it trough a power regulator.
That only allows it to be powered with 7-12 volts, but i want an option to power it with the 5v output of another Arduino uno (the Uno as ISP); that's why i need a regulated 5v input pin.

Does anybody know how to do it? Thanks in advance.

Post your schematic.

If the output of the other power source is regulated, you don't need to regulate the input.

The 5V output of an Uno is regulated, either via its voltage regulator or from the USB.

Schottky diode from usb-5v to 5v rail, and external 5v power to 5v rail directly.

Easypeasy.

So all i need to do is putting a diode between the 5v rail and the output pin on the regulator. Than i can just connect the regulated 5v directly to the 5v rail…

Thanks for the responses.