The USI WM-N-BM-14 has a STM32F205 + BCM43362.
The platform definitions from .../Wiced/Platform/<platform>/platform.c are used by the .../Wiced/Platform/common/<ARM_Cortex_Mx>/<MCU>/<MCU>_platform.c.
For specific to BCM9WCDPLUS114 uart setup for BT and WiFi module the uart is setup as follow:
The bt_bus_init() in ...\Library\bluetooth\internal\bus\UART\bt_bus.c called from wiced_bt_init() which is called from application_start(). The BLUETOOTH_UART is defined as WICED_UART_2 and corresponds to the uart_mapping definitions in .../Wiced/Platform/BCM9WCDPLUS114/platform.c
Hope it helps.