arch/risc-v/eic7700x: Describe the clock tree.

arch/risc-v/src/eic7700x/Kconfig

@@ -0,0 +1,23 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+comment "EIC7700X Configuration Options"
+
+config EIC7700X_CLK
+	bool "CRG clock provider"
+	default y
+	select CLK
+	---help---
+		Register the Clock and Reset Generator (CRG) clock tree with the
+		NuttX clock framework.  Registration itself writes nothing: the
+		tree comes up describing the PLL, mux, divider and gate
+		configuration the boot loader left behind.  The tree is visible
+		through /proc/clk when procfs is enabled.
+
+		A clock moves only when a driver asks it to, by enabling a gate,
+		setting a divider, or reparenting a mux.  A mux that carries a
+		clock the system is running on will speed up on request but
+		refuses to slow down, since that would change the timing every
+		driver downstream was configured for while they are using it.

arch/risc-v/src/eic7700x/Make.defs

@@ -30,3 +30,7 @@ HEAD_ASRC = eic7700x_head.S
 CHIP_CSRCS  = eic7700x_start.c eic7700x_irq_dispatch.c eic7700x_irq.c
 CHIP_CSRCS += eic7700x_timerisr.c eic7700x_allocateheap.c
 CHIP_CSRCS += eic7700x_mm_init.c eic7700x_pgalloc.c
+
+ifeq ($(CONFIG_EIC7700X_CLK),y)
+CHIP_CSRCS += eic7700x_clk.c eic7700x_clk_ops.c
+endif