diff -drupN a/include/linux/of_fdt.h b/include/linux/of_fdt.h
--- a/include/linux/of_fdt.h	2018-08-06 17:23:04.000000000 +0300
+++ b/include/linux/of_fdt.h	2022-06-12 05:28:14.000000000 +0300
@@ -63,6 +63,27 @@ extern int of_flat_dt_match(unsigned lon
 extern unsigned long of_get_flat_dt_root(void);
 extern int of_get_flat_dt_size(void);
 
+/*
+ * early_init_dt_scan_chosen - scan the device tree for ramdisk and bootargs
+ *
+ * The boot arguments will be placed into the memory pointed to by @data.
+ * That memory should be COMMAND_LINE_SIZE big and initialized to be a valid
+ * (possibly empty) string.  Logic for what will be in @data after this
+ * function finishes:
+ *
+ * - CONFIG_CMDLINE_FORCE=true
+ *     CONFIG_CMDLINE
+ * - CONFIG_CMDLINE_EXTEND=true, @data is non-empty string
+ *     @data + dt bootargs (even if dt bootargs are empty)
+ * - CONFIG_CMDLINE_EXTEND=true, @data is empty string
+ *     CONFIG_CMDLINE + dt bootargs (even if dt bootargs are empty)
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=non-empty:
+ *     dt bootargs
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is non-empty string
+ *     @data is left unchanged
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is empty string
+ *     CONFIG_CMDLINE (or "" if that's not defined)
+ */
 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);
 extern int early_init_dt_scan_memory(unsigned long node, const char *uname,