Add some documentation of the prctl(PR_FUTEX_HASH, …) interface.
The PR_FUTEX_HASH interface has been merged during the merge window,
v6.16-rc1 is expected this weekend.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v3…v4: https://lore.kernel.org/all/20250526155523.1382465-1-bigeasy@linutronix.de/
  - Make FH_FLAG_IMMUTABLE and CONFIG_PROVE_LOCKING bold.
  - Drop one too many "Relative inset"
  - Reword return value for "GET_IMMUTABLE"
  - Reword the description of "unrelated futexes" in PR_FUTEX_HASH

v2…v3: https://lore.kernel.org/all/20250520104247.S-gVcgxM@linutronix.de/
  - Split the individual PR_FUTEX_HASH ops into their own man page.
  - Reword a sentence referring to uaddr in order to link to futex(2).
  - Address remaining review feedback such the semantic new line.

v1…v2: https://lore.kernel.org/all/20250516161422.BqmdlxlF@linutronix.de/
  - Partly reword
  - Use "semantic newlines"

Sebastian Andrzej Siewior (4):
  man/man2/prctl.2, man/man2const/PR_FUTEX_HASH.2const: Document
    PR_FUTEX_HASH
  man/man2/prctl.2, PR_FUTEX_HASH_SET_SLOTS.2const: Document
    PR_FUTEX_HASH_SET_SLOTS
  man/man2/prctl.2, PR_FUTEX_HASH_GET_SLOTS.2const: Document
    PR_FUTEX_HASH_GET_SLOTS
  man/man2/prctl.2, PR_FUTEX_HASH_GET_IMMUTABLE.2const: Document
    PR_FUTEX_HASH_GET_IMMUTABLE

 man/man2/prctl.2                              |  3 +
 man/man2const/PR_FUTEX_HASH.2const            | 89 +++++++++++++++++++
 .../PR_FUTEX_HASH_GET_IMMUTABLE.2const        | 39 ++++++++
 man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const  | 37 ++++++++
 man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const  | 82 +++++++++++++++++
 5 files changed, 250 insertions(+)
 create mode 100644 man/man2const/PR_FUTEX_HASH.2const
 create mode 100644 man/man2const/PR_FUTEX_HASH_GET_IMMUTABLE.2const
 create mode 100644 man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const
 create mode 100644 man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const

-- 
2.49.0