Merge branch 'net-make-timestamping-selectable'

Merge branch 'net-make-timestamping-selectable'

Kory Maincent says:

====================
net: Make timestamping selectable

Up until now, there was no way to let the user select the layer at
which time stamping occurs. The stack assumed that PHY time stamping
is always preferred, but some MAC/PHY combinations were buggy.

This series updates the default MAC/PHY default timestamping and aims to
allow the user to select the desired layer administratively.

Changes in v2:
- Move selected_timestamping_layer variable of the concerned patch.
- Use sysfs_streq instead of strmcmp.
- Use the PHY timestamp only if available.

Changes in v3:
- Expose the PTP choice to ethtool instead of sysfs.
  You can test it with the ethtool source on branch feature_ptp of:
  https://github.com/kmaincent/ethtool
- Added a devicetree binding to select the preferred timestamp.

Changes in v4:
- Move on to ethtool netlink instead of ioctl.
- Add a netdev notifier to allow packet trapping by the MAC in case of PHY
  time stamping.
- Add a PHY whitelist to not break the old PHY default time-stamping
  preference API.

Changes in v5:
- Update to ndo_hwstamp_get/set. This bring several new patches.
- Add few patches to make the glue.
- Convert macb to ndo_hwstamp_get/set.
- Add netlink specs description of new ethtool commands.
- Removed netdev notifier.
- Split the patches that expose the timestamping to userspace to separate
  the core and ethtool development.
- Add description of software timestamping.
- Convert PHYs hwtstamp callback to use kernel_hwtstamp_config.

Changes in v6:
- Few fixes from the reviews.
- Replace the allowlist to default_timestamp flag to know which phy is
  using old API behavior.
- Rename the timestamping layer enum values.
- Move to a simple enum instead of the mix between enum and bitfield.
- Update ts_info and ts-set in software timestamping case.

Changes in v7:
- Fix a temporary build error.
- Link to v6: https://lore.kernel.org/r/20231019-feature_ptp_netnext-v6-0-71affc27b0e5@bootlin.com
====================

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>