dt-bindings: mvebu-uart: update information about UART clock

Device "marvell,armada-3700-uart" should use
"marvell,armada-3700-uart-clock" compatible clock.
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NMarek Behún <kabel@kernel.org>
Reviewed-by: NStephen Boyd <sboyd@kernel.org>
Signed-off-by: NPali Rohár <pali@kernel.org>
Signed-off-by: NMarek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20220219152818.4319-5-kabel@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/mvebu-uart.txt

@@ -14,7 +14,10 @@ Required properties:
       is provided (possible only with the "marvell,armada-3700-uart"
       compatible string for backward compatibility), it will only work
       if the baudrate was initialized by the bootloader and no baudrate
-      change will then be possible.
+      change will then be possible. When provided it should be UART1-clk
+      for standard variant of UART and UART2-clk for extended variant
+      of UART. TBG clock (with UART TBG divisors d1=d2=1) or xtal clock
+      should not be used and are supported only for backward compatibility.
 - interrupts:
     - Must contain three elements for the standard variant of the IP
       (marvell,armada-3700-uart): "uart-sum", "uart-tx" and "uart-rx",
@@ -34,7 +37,7 @@ Example:
 	uart0: serial@12000 {
 		compatible = "marvell,armada-3700-uart";
 		reg = <0x12000 0x18>;
-		clocks = <&xtalclk>;
+		clocks = <&uartclk 0>;
 		interrupts =
 		<GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>,
 		<GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
@@ -45,7 +48,7 @@ Example:
 	uart1: serial@12200 {
 		compatible = "marvell,armada-3700-uart-ext";
 		reg = <0x12200 0x30>;
-		clocks = <&xtalclk>;
+		clocks = <&uartclk 1>;
 		interrupts =
 		<GIC_SPI 30 IRQ_TYPE_EDGE_RISING>,
 		<GIC_SPI 31 IRQ_TYPE_EDGE_RISING>;