The issue was that these variables in the kernel config were set to 10. Setting them to 12 allowed uart10 to initilaize.
CONFIG_SERIAL_8250_NR_UARTS=12
CONFIG_SERIAL_8250_RUNTIME_UARTS=12
I'm trying to enable UART6, UART7, and UART10 via overlays on a sige5 board. UART6 AND UART7 are working fine but I'm not seeing UART10 in the /dev directory. Could someone help me debug this?