I also had some Makefiles in other directories, e.g., for my media/ I had:

MAKE = make -s
RECURS = svgs/

recurs: $(RECURS)
        @$(foreach DIR, $(RECURS), \
                echo "MAKE      (CD)    $(CURDIR)/$(DIR)"; \
                $(MAKE) -C $(DIR) $(MAKECMDGOALS);)
        @echo "MAKE     (CD)    $(CURDIR)/"

all: recurs

clean:

allclean: recurs clean

and for media/svgs/:

SVG_FILES := $(wildcard *.svg)
PDFDIR := ./
PDF_FILES := $(patsubst %.svg,$(PDFDIR)/%.pdf,$(SVG_FILES))

all: $(PDF_FILES)

clean:
        @rm -f $(PDF_FILES)
        @echo "SH       (RM)    Tidying up derived PDFs"

allclean: clean

$(PDFDIR)/%.pdf: %.svg
        @inkscape -T --export-pdf=$@ $<
        @echo "INK      (PDF)   $<"