✅ Build completed.

⬇️ Build URL: http://downloads.arduino.cc/PR/samd/package_samd-b200_index.json

ℹ️ To test this build:

1. Open the Preferences of the Arduino IDE.
2. Add the Build URL above in the Additional Boards Manager URLs field, and click OK.
3. Open the Boards Manager (menu Tools->Board->Board Manager...)
4. Install Arduino SAMD core - Pull Request MKR boards: I2C to sercom2, SPI1 + Serial2 to sercom4 #378
5. Select one of the boards under SAMD Pull Request MKR boards: I2C to sercom2, SPI1 + Serial2 to sercom4 #378 in Tools->Board menu
6. Compile/Upload as usual

@sandeepmistry tested both SPI and I2C by using the examples of each boards and a I2C sensors and all goes fine, ok for me

What is the purpose of this change? The OP says "so that sercom can be used for alternative purposes". What "alternative purposes" are you referring to?

What "alternative purposes" are you referring to?

Adding an additional SPI interface on pins A3 + A4 to use in conjunction with the new MKR RGB shield.

Late to the game, but the labels in the MKRWiFi1010V2.0 schematics (ABX00023-schematics.pdf) still reflect the old sercom numbers. Confused me no end (was there a board revision I had missed?), until I traced back this commit and the reasoning behind it (which helped me a lot in fact, as I needed two extra sercoms on the digital pins badly, so thanks!).

Don't know where else I should report docs issues....