On Fri, Dec 10, 2021 at 10:19 AM Yann Gautier [off-list ref] wrote:

Although this compatible is not used in kernel, as we use the common
MMCI driver, it is used by bootloaders. The U-Boot driver was merged
before the kernel driver and uses this compatible.
To avoid issues when aligning device tree files between kernel and
boot loader, the ST dedicated compatible is added to bindings file.

Signed-off-by: Yann Gautier <redacted>

Why not
Acked-by: Linus Walleij <redacted>

+      - description: Entry for STMicroelectronics variant of PL18x.
+          This dedicated compatible is used by bootloaders.
+        items:
+          - const: st,stm32-sdmmc2
+          - const: arm,pl18x
+          - const: arm,primecell

You *could* mark it deprecated if it's not supposed to be used.
But no strong opinion.

Yours,
Linus Walleij