Applying ShadowNinja recommendation

See https://github.com/minetest/minetest_game/pull/307#issuecomment-53363617

mods/carpet/init.lua

@@ -1,27 +1,33 @@
+-- Carpet API
 carpet = {}
 
--- Carpet API
+-- Registering carpet ( carpet.register() )
 --[[
+	def is a table that contains:
 	name		: itemstring "carpet:name"
-	desc		: node description
+	description	: node description (optional)
 	images		: node tiles
 	recipeitem	: node crafting recipeitem {recipeitem,recipeitem}
 	groups		: node groups
-	sounds		: node sounds
+	sounds		: node sounds (optional)
 --]]
 -- Carpet will be named carpet:name
-function carpet.add(name, desc, images, recipeitem, groups, sounds)
+function carpet.register(def)
+	local name = def.name
+	local desc = def.description or ""
+	local recipeitem = def.recipeitem
+	local sounds = def.sounds or default.node_sound_defaults()
 	-- Node Definition
 	minetest.register_node("carpet:"..name, {
 		description = desc,
-		tiles = images,
+		tiles = def.images,
 		paramtype = "light",
 		node_box = {
 			type = "fixed",
 			fixed = {-0.5, -0.5, -0.5, 0.5, -7/16, 0.5},
 		},
 		drawtype = "nodebox",
-		groups = groups,
+		groups = def.groups,
 		sounds = sounds,
 	})
 	-- Crafting Definition
@@ -55,10 +61,12 @@ carpet.wool = {
 for _, row in ipairs(carpet.wool) do
 	local name = row[1]
 	local desc = row[2]
-	carpet.add(
-		name, desc..' Carpet',
-		{'wool_'..name..'.png'}, 'wool:'..name,
-		{snappy=2,choppy=2,oddly_breakable_by_hand=3,flammable=3,falling_node=1,carpet=1},
-		default.node_sound_defaults()
-	)
+	carpet.register({
+		name = name,
+		description = desc..' Carpet',
+		images = {'wool_'..name..'.png'},
+		recipeitem = 'wool:'..name,
+		groups = {snappy=2,choppy=2,oddly_breakable_by_hand=3,flammable=3,falling_node=1,carpet=1},
+		sounds = default.node_sound_defaults()
+	})
 end