ARM: dts: define clock binding for bcm21664

Document the device tree binding for Broadcom BCM28164 clock control
units and clocks. This SoC uses Kona CCUs, similar to the BCM281XX
SoC family.

Signed-off-by: Alex Elder <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

Documentation/devicetree/bindings/clock/bcm-kona-clock.txt

···
     slave   bsc2            peri      7     BCM281XX_SLAVE_CCU_BSC2
     slave   bsc3            peri      8     BCM281XX_SLAVE_CCU_BSC3
     slave   pwm             peri      9     BCM281XX_SLAVE_CCU_PWM
+
+
+BCM21664 family
+---------------
+CCU compatible string values for SoCs in the BCM21664 family are:
+    "brcm,bcm21664-root-ccu"
+    "brcm,bcm21664-aon-ccu"
+    "brcm,bcm21664-master-ccu"
+    "brcm,bcm21664-slave-ccu"
+
+The following table defines the set of CCUs and clock specifiers for
+BCM21664 family clocks.  When a clock consumer references a clocks,
+its symbolic specifier (rather than its numeric index value) should
+be used.  These specifiers are defined in:
+    "include/dt-bindings/clock/bcm21664.h"
+
+    CCU     Clock           Type    Index   Specifier
+    ---     -----           ----    -----   ---------
+    root    frac_1m         peri      0     BCM21664_ROOT_CCU_FRAC_1M
+
+    aon     hub_timer       peri      0     BCM21664_AON_CCU_HUB_TIMER
+
+    master  sdio1           peri      0     BCM21664_MASTER_CCU_SDIO1
+    master  sdio2           peri      1     BCM21664_MASTER_CCU_SDIO2
+    master  sdio3           peri      2     BCM21664_MASTER_CCU_SDIO3
+    master  sdio4           peri      3     BCM21664_MASTER_CCU_SDIO4
+    master  sdio1_sleep     peri      4     BCM21664_MASTER_CCU_SDIO1_SLEEP
+    master  sdio2_sleep     peri      5     BCM21664_MASTER_CCU_SDIO2_SLEEP
+    master  sdio3_sleep     peri      6     BCM21664_MASTER_CCU_SDIO3_SLEEP
+    master  sdio4_sleep     peri      7     BCM21664_MASTER_CCU_SDIO4_SLEEP
+
+    slave   uartb           peri      0     BCM21664_SLAVE_CCU_UARTB
+    slave   uartb2          peri      1     BCM21664_SLAVE_CCU_UARTB2
+    slave   uartb3          peri      2     BCM21664_SLAVE_CCU_UARTB3
+    slave   uartb4          peri      3     BCM21664_SLAVE_CCU_UARTB4
+    slave   bsc1            peri      4     BCM21664_SLAVE_CCU_BSC1
+    slave   bsc2            peri      5     BCM21664_SLAVE_CCU_BSC2
+    slave   bsc3            peri      6     BCM21664_SLAVE_CCU_BSC3
+    slave   bsc4            peri      7     BCM21664_SLAVE_CCU_BSC4