linuxrc: part keyword

Clean up documentation and functionality of "part" argument to
initramfs. It is meant to imitate the same option to the kernel.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

defaults/linuxrc

@@ -156,6 +156,9 @@ do
 		part=*)
 			MDPART=${x#*=}
 		;;
+		part|partitionable)
+			MDPART=1
+		;;
 		# NFS
 		ip=*)
 			IP=${x#*=}

doc/genkernel.8.txt

@@ -520,12 +520,10 @@ which the ramdisk scripts would recognize.
 *console*=<...>::
     Override location of console, default is "/dev/console".
 
-*part*=<...>::
-    Specify part for mdadm to start.  This is the relevant code in mdstart:
-------------------------------------------
-    fd = open("/dev/md<MD_NUMBER>", 0, 0);
-    ioctl(fd, RAID_AUTORUN, <MDPART>);
-------------------------------------------
+*part*[=<0,1>]::
+*partitionable*::
+	Enable/Disable partitionable RAIDs (metadata 0.x) during auto-run.
+	Standalone *part* and *partitionable* keywords for kernel compatability.
 
 *iscsi_initiatorname*=<...>::
 *iscsi_target*=<...>::