qemu-system-x86_64 help does not provide info about pflash0 and pflash1

Description of problem

Command

qemu-system-x86_64 -machine pc-q35-9.2,help

Does not provide any clue about pflash0 and pflash1 arguments existence while these arguments are present, mentioned in various docs and extensively used by projects like libvirt:

https://www.qemu.org/docs/master/system/introduction.html

https://gitlab.com/qemu-project/qemu/-/blob/staging-10.0/docs/interop/firmware.json?ref_type=heads#L317

https://gitlab.com/qemu-project/qemu/-/blob/staging-10.0/docs/interop/firmware.json?ref_type=heads#L338

Host environment

• Operating system:

  Ubuntu 25.10

• OS/kernel version:

  Linux Gram 6.17.0-8-generic #8-Ubuntu SMP PREEMPT_DYNAMIC Fri Nov 14 21:44:46 UTC 2025 x86_64 GNU/Linux

• Architecture:

  x86

• QEMU flavor:

  qemu-system-x86_64

• QEMU version:

  QEMU emulator version 10.1.0 (Debian 1:10.1.0+ds-5ubuntu2.1)

• QEMU command line:

  qemu-system-x86_64 -machine pc-q35-9.2,help