cpufreq: Update Documentation for cpus and related_cpus

Documentation related to cpus and related_cpus is confusing and not very clear.
Over that CPUFreq core has seen much changes recently. Lets update documentation
and comments for cpus and related_cpus.

Signed-off-by: Viresh Kumar <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

Documentation/cpu-freq/cpu-drivers.txt

···
 For setting some of these values, the frequency table helpers might be
 helpful. See the section 2 for more information on them.
 
+SMP systems normally have same clock source for a group of cpus. For these the
+.init() would be called only once for the first online cpu. Here the .init()
+routine must initialize policy->cpus with mask of all possible cpus (Online +
+Offline) that share the clock. Then the core would copy this mask onto
+policy->related_cpus and will reset policy->cpus to carry only online cpus.
+
 
 1.3 verify
 ------------

Documentation/cpu-freq/user-guide.txt

···
 				first set scaling_max_freq, then
 				scaling_min_freq.
 
-affected_cpus :			List of CPUs that require software coordination
-				of frequency.
+affected_cpus :			List of Online CPUs that require software
+				coordination of frequency.
 
-related_cpus :			List of CPUs that need some sort of frequency
-				coordination, whether software or hardware.
+related_cpus :			List of Online + Offline CPUs that need software
+				coordination of frequency.
 
 scaling_driver :		Hardware driver for cpufreq.
 

include/linux/cpufreq.h

···
 };
 
 struct cpufreq_policy {
-	cpumask_var_t		cpus;	/* CPUs requiring sw coordination */
-	cpumask_var_t		related_cpus; /* CPUs with any coordination */
+	/* CPUs sharing clock, require sw coordination */
+	cpumask_var_t		cpus;	/* Online CPUs only */
+	cpumask_var_t		related_cpus; /* Online + Offline CPUs */
+
 	unsigned int		shared_type; /* ANY or ALL affected CPUs
 						should set cpufreq */
 	unsigned int		cpu;    /* cpu nr of CPU managing this policy */