3.15.11 Boot Manager BootNext Processing

After connecting any drivers in the DriverOrder list, the platform boot manager attempts to boot the option that is specified by the BootNext environment variable. This environment variable is discussed in the Boot Manager chapter of the UEFI Specification. This variable typically is not set, but if it is, the platform firmware deletes the variable and then attempts to load the boot option that is described in the Boot#### variable pointed to by BootNext.
Before the platform boot manager boots the boot option, it uses the device path stored in the Boot#### variable to connect the controllers and drivers that are required to access the boot option. This process is exactly the same as the process that is used for the console variables ErrOut, ConOut, and ConIn.