net: stmmac: rename devlink parameter ts_coarse into phc_coarse_adj

The devlink param "ts_coarse" doesn't indicate that we get coarse
timestamps, but rather that the PHC clock adjusments are coarse as the
frequency won't be continuously adjusted. Adjust the devlink parameter
name to reflect that.

The Coarse terminlogy comes from the dwmac register naming, update the
documentation to better explain what the parameter is about.

With this change, the parameter can now be adjusted using:
devlink dev param set <dev> name phc_coarse_adj value true cmode runtime

Signed-off-by: Maxime Chevallier <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/networking/devlink/stmmac.rst

···
      - Type
      - Mode
      - Description
-   * - ``ts_coarse``
+   * - ``phc_coarse_adj``
      - Boolean
      - runtime
-     - Enable the Coarse timestamping mode. In Coarse mode, the ptp clock is
-       expected to be updated through an external PPS input, but the subsecond
-       increment used for timestamping is set to 1/ptp_clock_rate. In Fine mode
-       (i.e. Coarse mode == false), the ptp clock frequency is adjusted more
-       frequently, but the subsecond increment is set to 2/ptp_clock_rate.
+     - Enable the Coarse timestamping mode, as defined in the DWMAC TRM.
+       A detailed explanation of this timestamping mode can be found in the
+       Socfpga Functionnal Description [1].
+
+       In Coarse mode, the ptp clock is expected to be fed by a high-precision
+       clock that is externally adjusted, and the subsecond increment used for
+       timestamping is set to 1/ptp_clock_rate.
+
+       In Fine mode (i.e. Coarse mode == false), the ptp clock frequency is
+       continuously adjusted, but the subsecond increment is set to
+       2/ptp_clock_rate.
+
        Coarse mode is suitable for PTP Grand Master operation. If unsure, leave
        the parameter to False.
+
+       [1] https://www.intel.com/content/www/us/en/docs/programmable/683126/21-2/functional-description-of-the-emac.html

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

···
 }
 
 static const struct devlink_param stmmac_devlink_params[] = {
-	DEVLINK_PARAM_DRIVER(STMMAC_DEVLINK_PARAM_ID_TS_COARSE, "ts_coarse",
+	DEVLINK_PARAM_DRIVER(STMMAC_DEVLINK_PARAM_ID_TS_COARSE, "phc_coarse_adj",
 			     DEVLINK_PARAM_TYPE_BOOL,
 			     BIT(DEVLINK_PARAM_CMODE_RUNTIME),
 			     stmmac_dl_ts_coarse_get,