I'm bringing the conversation from https://github.com/apache/mynewt-core/pull/564#issuecomment-331137397 to a larger audience, per wes3's suggestion.
The question is whether to move some syscfg definitions that are duplicated across many BSPs into MCUs instead. The definitions in this case are I2C_0, I2C_1, SPI_0_MASTER, and SPI_0_SLAVE. Their primary use seems to be in the MCU, where they are checked when instantiating these interfaces, but they are also used in the BSPs for initialization with board specific pin numbers. In the PR above I added a restriction between the I2C and SPI definitions as dictated by the nRF52. I only added it for the EE-02 board, but it really should be done for all nRF52 based boards. Duplication could be avoided by moving these definitions into the MCUs. What do you think?
