Mbox Meson Ref -

While it looks like a cryptic developer error, It surfaces on your TV or receiver through a communication protocol called HDMI-CEC (Consumer Electronics Control).

Identifies the hardware driver (MHU - Mailbox Handling Unit). reg : The physical memory address of the mailbox hardware. mbox meson ref

: Developers working with Armbian or custom Linux builds on S905 chipsets encounter this string in U-Boot (the bootloader) during the initial stages of hardware initialization. Actionable Summary While it looks like a cryptic developer error,

Use the Device Tree compiler utilities ( fdtget / fdtput ) to rewrite the product description variable embedded in the HDMI transmitter ( amhdmitx ) nodes: mbox meson ref