Hi, I allready tried with no kernel parameters set. I found those options used in other Toshiba notebooks.
Following your request I tried again. I removed the post-down option and those kernel parameters: the Realtek controller disappeared again.
root@zbox:~# dmesg|head -n 20
[ 0.000000] microcode: microcode updated early to revision 0x4, date = 2013-06-28
[ 0.000000] Linux version 4.9.0-1-amd64 (
debian-kernel@lists.debian.org) (gcc version 6.3.0 20161229 (Debian 6.3.0-2) ) #1 SMP Debian 4.9.2-2 (2017-01-12)
[ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-4.9.0-1-amd64 root=UUID=5a0b32cc-2aaf-4c3f-a33a-425168aab3e7 ro intel_pstate=disable
[ 0.000000] Disabled fast string operations
[ 0.000000] x86/fpu: Legacy x87 FPU detected.
[ 0.000000] x86/fpu: Using 'eager' FPU context switches.
[ 0.000000] e820: BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009d7ff] usable
[ 0.000000] BIOS-e820: [mem 0x000000000009d800-0x000000000009ffff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bb30efff] usable
[ 0.000000] BIOS-e820: [mem 0x00000000bb30f000-0x00000000bb690fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bb691000-0x00000000bb69efff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bb69f000-0x00000000bb6a1fff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bb6a2000-0x00000000bb6a4fff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bb6a5000-0x00000000bb6acfff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bb6ad000-0x00000000bb6ccfff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bb6cd000-0x00000000bb70efff] reserved
[ 0.000000] BIOS-e820: [mem 0x00000000bb70f000-0x00000000bb70ffff] ACPI NVS
[ 0.000000] BIOS-e820: [mem 0x00000000bb710000-0x00000000bb714fff] reserved