For one of my project the controller selection made was STM32L1 series. ST provides the drivers for USB, I2C, SPI etc. So while making a decision on RTOS is there any consideration needed to be given to the drivers. Or in another way after deciding an RTOS, is there any standard way of interfacing peripheral drivers of the microcontroller with RTOS?
No, microcontroller peripheral drivers and the RTOS are typically independent so compatibility doesn't need to be a consideration. The microcontroller peripheral drivers are basic drivers that aren't reliant on any RTOS services. In fact the peripheral library can be used without any RTOS. And an RTOS typically does not rely on any microcontroller peripherals beyond a timer. Even the setup of the timer is not built-in to the RTOS. The timer is typically setup by user code, before starting the RTOS.
If I haven't convinced you and you still want some assurance of compatibility then explore CMSIS.