of: support passing console options with stdout-path

Support specifying console options (like with console=ttyXN,<options>)
by appending them to the stdout-path property after a separating ':'.

Example:
        stdout-path = "uart0:115200";
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
[grant.likely: minor rework to shorten the diffstat]
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/base.c

@@ -37,6 +37,7 @@ EXPORT_SYMBOL(of_root);
 struct device_node *of_chosen;
 struct device_node *of_aliases;
 struct device_node *of_stdout;
+static const char *of_stdout_options;
 
 struct kset *of_kset;
 
@@ -1852,7 +1853,7 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
 		if (IS_ENABLED(CONFIG_PPC) && !name)
 			name = of_get_property(of_aliases, "stdout", NULL);
 		if (name)
-			of_stdout = of_find_node_by_path(name);
+			of_stdout = of_find_node_opts_by_path(name, &of_stdout_options);
 	}
 
 	if (!of_aliases)
@@ -1978,7 +1979,8 @@ bool of_console_check(struct device_node *dn, char *name, int index)
 {
 	if (!dn || dn != of_stdout || console_set_on_cmdline)
 		return false;
-	return !add_preferred_console(name, index, NULL);
+	return !add_preferred_console(name, index,
+				      kstrdup(of_stdout_options, GFP_KERNEL));
 }
 EXPORT_SYMBOL_GPL(of_console_check);