Summary:
Placing a second Nether Portal in the Overworld returns you to the first one upon exiting the Nether

Steps to Reproduce:
1. Create a Nether Portal in the Overworld
2. Enter the Nether to take note of location
3. Return to Overworld
4. Travel 100 blocks away from the original portal
5. Build new Nether Portal
6. Enter Nether

Observed Result:
Arrive at the location of the original portal in the Nether
Upon exiting through the portal, arrive at the original portal location in Overworld