Add Peripheral RTM (P4) connector pinout recommendation
I took some inspiration from FMC and MTCA.4 standards.
- VCC_RTM - is +12V by default but can be a different voltage depending on the RTM/Peripheral board design
- P3V3 - is a low power (max 300mA) mainly to be used by identification EEPROM connected to SCL/SDA lines
- VIO - is the equivalent of Vadj in FMC, it's a voltage for powering the I/O buffers to match peripheral board voltage (in the case of DI/OT Peripheral FMC Carrier it's 2.5V)
- SCL/SDA - identification I2C, connected together with the main backplane I2C on Peripheral Board.
- RST_N - reset line from the P1 backplane connector
- PS# - RTM presence detection
- TRST/TDO/TDI/TMS/TCK - pins reserved for JTAG, if RTM/Peripheral board doesn't have JTAG capabilities it shall tie TDI with TDO
- all the rest are general purpose I/Os, GND, RTM_BUS, Vext1/2 - all were already defined in current specification.