Further to the above post and in the spirit of 4 dogs I went and found the applicable quotes from EASA CS-25 (current). The bolding is my own.
EASA CS-25 AMC 25.1581 - 6 (c)
c. Operating Procedures Section. The Operating Procedures Section of the AFM should contain, as a minimum, the essential information, peculiar to the particular aeroplane type design , that is needed for safe operation under normal and other-than-normal conditions. Procedures not directly
related to airworthiness, or not under control of the flight crew, should not be included in the AFM. A notation similar to the following should be placed at the beginning of the Operating Procedures Section.
The operating procedures contained in this manual have been developed and recommended by the manufacturer and approved by the EASA for use in operating this aeroplane. These procedures are provided as guidance and should not be construed as prohibiting the operator from developing equivalent procedures in accordance with the applicable operating rules.
And EASA AMC 25.1581 - 6 (c) (4) (ii)
(ii) Other Sources of Procedures Information. The flight crew of large transport category aeroplanes typically use other sources of operating procedures information other than the AFM. Examples of other sources of operating procedures information include manufacturer- or operatorproduced
operating manuals, Quick Reference Handbooks (QRH), System Pilot’s Guides and Emergency or Abnormal Checklists. For these aeroplanes, items such as cockpit checklists, systems descriptions, and the associated normal procedures should not be presented in the AFM if they are provided in other documents acceptable to the Agency. Normal procedures that are necessary for safe operation should be presented in the AFM, but the remaining normal procedures should be placed in the manufacturer produced FCOM (or other acceptable sources of operating procedures information).
The non-normal procedures section of the AFM for these types of aeroplanes should include, as a minimum, procedures dictated by the aeroplane’s system and failure modes, and may also include those emergency procedures listed in paragraph 6.c(5) of this AMC. Whenever procedures are provided in another source rather than the AFM, a statement should be placed in the appropriate
procedures section of the AFM referencing where the detailed procedures information can be found.