Amlogic Meson8, Meson8b and Meson8m2 SoCs have a DDR clock controller in the MMCBUS registers. There is no public documentation on this, but the GPL u-boot sources from the Amlogic BSP show that: - it uses the same XTAL input as the main clock controller - it contains a PLL which seems to be implemented just like the other PLLs in this SoC - there is a power-of-two PLL post-divider Add the documentation and header file for this DDR clock controller. Reviewed-by: Rob Herring <robh@kernel.org> Acked-by: Stephen Boyd <sboyd@kernel.org> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>